102 



GEOLOGICAL BIOLOGY. 





^&'s "'''&. 



r\U^ r^^ air r^ '^ Ci-. 



^ % f 7 





Fig. is. 



SchaiScfibi rqir.ggs. 



Fig. iS. 



Fig. 15. — Echinodermata, Crinoid. Taxocrtnus viultibrachiatus Ly. and Cass. Carboniferous. 

 Above: calyx with stem. Below: the plates of the calyx dissected, st = stem, br = free arms, air 

 = anal interradial plates ; rh = ri.5ht posterior, Ih = left posterior, vr = anterior right, ?'/ ^ 

 anterior left, vu = anterior medial radial plates ; ir/i = right posterior, ///; = left posterior, 

 irv = right anterior, i/z' = left anterior interradial plates ; z/, infrabasalia ; J>b = parabasalia ; 

 ri->-4 = radialia ; dl, dll — distichalia, first and second rank ; br = brachialia ; aj-ag, = anal 

 plates ; ir^-ir^ — larger interradial plates ; t — smaller interradial plates ; ss, plane of sym- 

 metry. (After S. and D ) 



Fig. 16. — Blastoid. Pentatremitidea £z/eliensis F. Rij. sp. Devonian, b = basalia ; r = 

 radialia ; / = ambulacra. (After S. and D.) 



Fig. 17. — Cystoid. Caryocrinus ornatus Say. Silurian. A, calyx with stem s \ br = arms ; I, 

 II, III, first, second, and third zones of plates of the dorsal capsule ; / = porous plates ; / = 

 place of attachment of arms ; a = anal opening B, view of the ventral dome, c= central 

 summit plates, i and a as above. C, inner surface of a plate of the second row, showing the 

 pores of the Hydrospires (/») and their connecting canal (d. (After S. and D.> 



Fig. 18. — Ophiuroi'd, A-H. Ophioceramis /erruginea Bohm. Jurassic. ,-!, a complete 

 specimen, from under side ; br ■=. arms. B = the disk from the inner side ; bb = bursal 

 shields ; / = ambulacral pores. C, mouth-skeleton from below; t/nu = mouth-angle; / = 

 papillae; vie = angle-plates; >ns= side shields; in = oral plates; b — second ventral plate. />, 

 disk from above; r = dorsal shield. £, a part of an arm from below; b = ventral shields; 

 J ^ lateral shields; / = ambulacral pores. 7% a part of an arm from above; r and j as above; 

 si — spines G, the same, lateral view. //, cross-section of an arm. /, Geocoma planata 

 Qu. sp.; bs ~ bursal slit; bb — bursal shield. (Steinmann and Doederlein.) 



