''Perkinsoceras''is an

endocerid Endocerida is an extinct nautiloid order, a group of cephalopods from the Lower Paleozoic with cone-like deposits in their siphuncle. Endocerida was a diverse group of cephalopods that lived from the Early Ordovician possibly to the Late Silurian ...

genus from the Middle Ordovician (Chazyan) of

Champlain Valley The Champlain Valley is a region of the United States around Lake Champlain in Vermont and New York extending north slightly into Quebec, Canada. It is part of the St. Lawrence River drainage basin, drained northward by the Richelieu River into ...

established by Flower in 1976, which he added to his Allotrioceratidae based on certain similarities to ''

Williamsoceras Williamsoceras is an endocerid that Rousseau Flower (1968) added to his Allotrioceratidae (Flower 1955) on the basis of having a vertical partition within the siphuncle, known as a ventral process, with inter-connecting tubule-like structure ...

'' and '' Cacheoceras'' which had been added previously. ''Perkinsoceras'' is characterized by a large ventral siphuncle in broad contact with the ventral margin of the phragmocone -the chambered portion of the shell- which is expanded into a '' Nanno'' type apex, and by a broad longitudinal ventral process about which the endocones are draped. ''Perkinsoceras'' has what have been interpreted as tubules that form where the endocones impinge on the process, a feature also interpreted in ''Williamsoceras'', ''Cacheoceras'' and the distinctly unique ''

Allotrioceras ''Allotrioceras'' is a tubular fossil from the Middle Ordovician of the state of New York, collected by Rousseau H. Flower; included by him in the Endocerida and placed in a new family, the Allotrioceratidae. ''Allotrioceras'' is characterized ...

'' ''Perkinsoceras'' differs from the generally similar '' Chazyoceras'' by its ventral process -absent in the latter, and by its more bulbous nanno type apex. ''Williamsoceras'' and ''Cacheoceras'' differ in having a straight cameroceras type apex without the expanded siphuncle. ''Allotrioceras'' differs by its vertical median partition separating the two lateral endocones. ''Perkinsoceras'' has a single set of endocones'' Two species of ''Perkinsoceras'' have been described, both early Middle Ordovician (Chazyan) in age, both from Vermont. ''P inflatum'' comes from the Crown Point Limestone, 1/2 mile south of Ferrisburg Vt. The holotype is in the Paleontology collection of th
New Mexico Museum of Natural History and Science
''P foerstei'' comes from Isle La Motte. Its holotype is at the U.S. National Museum in Washington D.C.

References

*Flower, R.H 1976. Some Whiterock and Chazy Endooceroids, Memoir 28, Part II, New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico *Flower, R. H. 1955. Status of Endoceroid Classification; Jour. Paleon. V 29. No.3, pp 327–370, May 1955 {{Taxonbar, from=Q7169070 Nautiloids

See also

References