Paryphanta Busbyi

''Paryphanta busbyi'' is a species of large predatory land snail, a terrestrial pulmonate gastropod mollusk in the family Rhytididae.

Distribution

The distribution of ''Paryphanta busbyi'' includes the Northern parts of North Island, New Zealand: Kaitaia, Hokianga, Mangōnui, Bay of Islands, Otonga East, Mania Hill, Whangārei, Brynderwyn Range, Hen Island, Woodcocks and Warkworth, which is its southern native distribution. Localitions with introduced distribution include Little Huia in Waitākere Ranges, Waiuku in Āwhitu Peninsula, and Kaimai Ranges.

Its distribution is coincident in range with the kauri forest.

The type locality is New Zealand. The type specimen is stored in Natural History Museum, London.

Shell description

The shell is large, broadly umbilicated, depressed and subdiscoidal. The shell is opaque and shining. The colour is deep green, usually with some radial streaks of blackish-green.

There is a sculpture on the nucleus containing oblique and arcuate radial plaits. The succeeding two whorls are distinctly rugose. On the post-embryonic whorls more or less distinct spiral cords appear, which are first directed upwards, but become spiral on the last whorl. Plaits are distant, low, broadly rounded, varying in number from about 5 to 10 and absent on the base. There are retractive distant growth-plications,
which are prominently and closely plicate at the suture. The whole surface of the shell is microscopically decussated by exceedingly fine and dense radiate and spiral lines, the latter slightly wavy. The periostracum is thick, glabrous, shining, overhanging the peristome. The spire is flat, very little raised and broadly convex. The protoconch has 2 whorls, flatly convex, the volutions rather rapidly increasing. The shell has 4½ whorls, that are rapidly increasing. The last whorl is very large, slightly convex, periphery and base rounded, the body-whorl more or less deflexed anteriorly. Suture well impressed.

The aperture is within shining-blue. Aperture obliquely lunate-oval. Peristome is simple, inflexed throughout. The columella is very oblique, slightly arcuate, and shortly reflexed above. Umbilicus broad, perspective and deep.

The width of the shell is 60–79 mm. The height of the shell is 33–44 mm.McGuinness C. A. (2001
''The conservation requirements of New Zealand’s nationally threatened invertebrates''
Threatened Species Occasional Publication 20. 658 pp. Page
71-120
The width of the type specimen is 66 × 53 mm, the height of the shell is 29 mm.

The shell of ''Paryphanta busbyi'' has very thick periostracum and only few micrometre thick calcium layer. When the shell is kept in dry environment, the shell will explode into pieces, because its periostracum shrinks.

The embryonic shell globose, flat above, of 2 whorls, narrowed toward the base and narrowly umbilicate. The width of the shell is 10 mm. The height of the shell is 9 mm.

Anatomy

The animal is bluish-black, with the foot-sole perhaps a shade lighter in colour. On the head and neck are a few regular rows of rugae, somewhat quadrate in outline; on other parts of the body the rugae appear to be oval-shaped, irregular in size, and not forming continuous rows. The mantle has a sharp even margin, and a deeply incised line or groove rather less than 2 mm from the edge. On the underside of the mantle is the usual prominent lappet which conceals the respiratory and anal pores, and in addition to this is a long narrow fold on the left side.

The retractor muscles: The buccal mass and pedal retractors are fused together posteriorly where they unite with the columella of the shell. The buccal retractor rests dorsally on the pedal muscles, and forms a broad powerful band. The pedal retractors are continuously attached to the foot, and there are no free progressively attached pedal retractors as in genus ''Helix''. The ocular retractors branch from the pedal muscles; they bifurcate towards their anterior ends, and supply the inferior tentacle retractors.

The length of the radula is about an inch, and 0.4 inch in width at the anterior end, tapering to a point posteriorly, with about 104 transverse rows of denticles (tiny teeth). The rows of denticles are forming an obtuse angle of about 130°, salient posteriorly. There is about 100 small denticles in each row, that described and figured by Captain Frederick Hutton with formula 50-0-50, while Robert C. Murdoch gave the formula 52-0-52. Hutton described them like this: Denticles are all aculeate, and similar, with simple bevelled tips. The first five lateral denticles are small. From the sixth they gradually increase in length to about the thirty-fifth, and then get smaller. Murdoch described them like this: A few of the innermost denticles, usually not more than two on each side, are small and very slender. Occasionally one of these slender spicula-like denticles is somewhat separated from the adjoining denticle, and where this occurs it gives to the row the appearance of a central denticle. There is no jaw.

The digestive system contains enormous buccal mass is and muscular development. Its posterior end is curved down and forward, and a powerful ventral muscle firmly binds it to the more anterior cylindrical portion. The retractor muscle envelopes the posterior end, and from the anterior portion of the mass proceed a number of ventro-lateral muscles, which unite with the immediately adjoining body-walls. The oesophagus enters the buccal cavity dorsally in the anterior fourth. The salivary glands are situate upon the posterior half of the buccal mass; they are fused together in the median line and partly envelope the oesophagus. From the anterior end of each gland proceeds a small salivary duct