. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. Mr. F. M'Coy on some neiv Palceozoic Echinodermata. 253 Russia and the Ural Mountains. Under those circumstances, therefore, it seems the most simple and correct course to use the term Archceocidaris for those fossils. The order Perischoechinida may be divided into two families : 1st, Palcpchinidce, having the interambulacral plates crowded with small, subequal, spinigerous tubercles, not perforated, the spines of one form (including Palcechinus, Melonites, Owen and Nor- wood,
. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. Mr. F. M'Coy on some neiv Palceozoic Echinodermata. 253 Russia and the Ural Mountains. Under those circumstances, therefore, it seems the most simple and correct course to use the term Archceocidaris for those fossils. The order Perischoechinida may be divided into two families : 1st, Palcpchinidce, having the interambulacral plates crowded with small, subequal, spinigerous tubercles, not perforated, the spines of one form (including Palcechinus, Melonites, Owen and Nor- wood, &c.); 2nd, ArchfEocidaridoi, having the spines and tubercles of two forms and sizes, the primary spines very large, generally muricated, crenulated at the base, and each supported on a large mammillated and perforated primary tubercle surrounded by an elevated ring, never more than one on any plate, generally sur- rounded by a crowd of the small secondary tubercles (including Archceocidaris, M'Coy, and the following). These family divi- sions rest on the same characters as the separation of the true Echini and the Cidarida among the normally formed Echinida. Perischodomus (M'Coy), n. g. Etym. Treptcr^cbv, complexus, and Sojfia, domus. Gen. Char. Spheroidal, depressed, subpentagonal; ambulacra narrow, of two rows of small plates, most usually of a trans- O O o <^ ° o. a. Diagram of portion of interambulacrum and ambulacra of Perischodomus, b. One of the primary and some of the secondary tubercles magnified more highly. c. One of the ovarian plates. versely elongate pentagonal figure, and each pierced by one pair of simple poi-es; interambulacra wide, of five rows of plates very irregular in size and shape, all the plates covered with small equal granules or secondary tubercles, while the row on each side adjoining the ambulacra alone bear the small, smooth primary spines, one on each, the supporting tubercle being small, mammillated, perforated, but not crenulated, sur-
Size: 2069px × 1208px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookce, booksubjectbotany, booksubjectgeology, booksubjectzoology
