PALEOZOIC TIME — CAMBRIAN. 



471 



5. Brachiopods. — The Articulate Brachiopods (or those in which the 

 valves are hinged together), as well as the Inarticulate, were represented, but 

 most abundantly the latter. Figs. 510-513, 515 represent some of the 

 species of the latter division, and Figs. 514, 516-520, some of the former. 



510. 



511. 



510-520. 

 511a. 



512. 



612 a. 



513 a. 



520 



519. 



518. 



Beachiopods. — Fig. 510, Lingulella ccslata, ventral (2) ; 511, L. ella, ventral (2); 511a, same, cast of interior 

 of dorsal valve (2) ; 512, Acrotreta gemma, side view (3); 512 a, same, upper view, ventral (3) ; 513, Obo- 

 lella crassa, dorsal (2): 513a, cast of interior of ventral (2); 514, Kutorgina cingulata, ventral; 515, 

 Iphidea bella; 516, Orthis (?) Highlandensis of Walcott, dorsal shell mostly worn oft" (1) ; 517, Orthisina 

 (Billingsella) festinata (i) ; 518, O. (B.) orientalis, ventral (1) ; 519, Orthis Salemensia, ventral ; 520, Camar- 

 ella (?) autiquata, ventral, enlarged. Figs, from Walcott; 510, 513, after Ford ; 518, after Whitfield ; 

 515, after Billings. 



6. Mollusks. — Figures 521, 522 represent species of Lamellibranchs, 

 each of very small size (here enlarged), and rare fossils ; and Figs. 523-525, 

 several Gastropods, cap-like in form, like the modern Patella. The Platy- 

 ceras primcevicm of Walcott (Fig. 526) has a short spiral at the summit, a 

 little like a broad horn, and hence the name, from the Greek ; the genus con- 

 tinues to the Carboniferous period, and, according to some authors, is not 

 generically distinct from the modern genus Capulus. Pleurotomaria Attle- 

 borensis is another Gastropod from North Attleborough, Mass. 



Other eminently characteristic Mollusks were the Pteropods of the genera 

 Hyolithes and Hyolithellus. They are long, conical, thin shells like Figs. 527, 

 528. The large end was closed by a shell-like operculum, one of which, of 

 the H. Americanus Walcott, is represented in Fig. 528 a. The Salterellae, 

 Figs. 529, 530, are stout shells, probably those of Pteropods. Fig. 529, S. 



