766 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



Plate 35. 



Pentacriiwid lartw of Hathrometra sarsii. {After M. Sars.) 



Fig. 1216. — Pentaerinoid at stage at which sis brachials are present. 



1217. — Pentaerinoid at stage at which pinnules are just beginning to appear. 

 1218. — Pentaerinoid at stage at which cirri are beginning to appear. 

 1219. — Fully developed pentaerinoid. 



Plate 36. 



Pentaerinoid lanw of Hathrometra sarsii. {After M. Sars.) 



Fig. 1220. — Most highly developed pentaerinoid obtained by Professor Sars. 

 1221. — Part of arm of same individual taken from middle. 

 1222. — Summit of column of fully developed individual. 



1223. — Tip of arm of young pentaerinoid, showing development of first pinnule to appear. 

 1224.— Sixth pinnule of individual shown in fig. 1220. 

 1225. — Disk of fully developed peut^icrinoid. 



Plate ."7. 



Fig. 1226. — Pentaerinoid of EeUometra glacialis. (After Levinsen.) 



1227. — Pentaerinoid of Hathrometra proHxa from Jan Mayen. (After P. H. Carpenter. I 



1228. — Pentaerinoid of Ptilometra miilleri. (After H. L. Clark.) 



1229.— Same. (After H. L. Clark.) 



1230.— Same. (After H. U Clark.) 



1231. — Abnormal arm of a specimen of Heliometra glacialis. (After Ijevinsen.) 



Plate 38. 



Pentaerinoid larim and pinnules of ririparons comatulifJs. (.After Th. Mortensen.) 



Fig. 1232. — Thaumatometra nutrix, a fully grown pent;ierinoid attached to third segment of 



genital pinnule; in ovary eggs are visible. 

 1233. — Thaumatometra nutrix, genital pinnule with young pentaerinoid attached to pinnule 



segment protruding through opening of the marsupium. 

 1234. — Thaumatometra nutrix, genital pinnule with two pentaeriuoids attached to third 



pinnule segment protruding from niarsupium. 

 1235. — Thaumatometra nutrix, type specimen, viewed dorsally; on one of arms to the left 



is genital pinnule bearing large pentaerinoid. 

 1236. — Thaumatometra nvtrix, genital pinnule with egg in marsupium. 

 1237. — Thaumatometra nutrix, genital pinnule with young pentaerinoid attached to extreme 



edge of marsupium. 

 1238. — Isometra viripara, genital pinnule viewed ventrally showing slitlike opening of 



marsupium. 

 1239. — Isometra tivipara, male genital pinnule. 

 1240. — Isometra viripara, proximal portion of arm, showing oral pinnules and extra fourth 



pinnula 



Plate 39. 



Commensals of Crinoids. 



Figs. 1241-1245. — Loxosomella antedonis. (After Mortensen.) 

 124G-1248. — Pachylasma crinoidophilum. (After Pilsbry.) 

 1249, 1250.— Ferruco n«i(to. (After Hoek.) 



