168 F. A. BATHER, ORINOIDEA OF GOTLAM). 



Gissocrinus incurvatus. 

 (Plate IX, tigs. 335, 336, and Plate X, figs. 337—351.) 



1878 Cyathocrinw incurvatus, Angelin, Iconographia, p. 23, Tab. XXVI, fig. 1. 



1N7<S Cyaihocrinus granulatus, Angelin, Iconographia. p. 23, Tab. XVI, figs. 1. 2 and 3. 



1879 Cyathocrinw incurvatus, Wachsmuth and Springer, Revision I, *r>. Proc. 1*79. p. 309. 

 1879 ? Arachnocrinus granulatus, Wachsmuth and Springer, Revision I, 93, Proc. 1879, p. 316. 



Diägnosis. 



Dorsal Cup very low and wide; its plates simply curved and ornamented with small 

 tubercles. IBP> ininute. BB half as. wide again as high. RR slightly wider than liigh; 

 facet 3/4ths widtli. IBr 1 (? sometimes 2). IIBr 1 or 2. Arms branch about 5 times; they 

 pass horizontally outwards from the calyx to the level of IIIBr; thon they curve round, 

 and when closed are markedly involute. Arm-ossicles have occasiona] tubercles, especially 

 oii the articular margins; they are slightly higher than wide, have broad slightly rounded 

 backs and flat sides sloping inwards. Ventral Sac horisontal; coraposed of hexagona] 

 plates which distall)' tend to run in transverse folds; the plates are rather prominent and 

 have slightly folded edges. Stera-ossicles round, low and alternating in height, the higher 

 ones projecting in rough ridges. 



There can be very little doubt but that C granulatus of Angelin, which Wachsmuth 

 and Springer have for some reason transferred to Arachnocrinus, is a svnonvm of this 

 speeies. The diägnosis tallies exactly. The type-specimen is said to be in the Riks- 

 museum, birt it cannot be found. The figures, however, agree with G. incurvatus in 

 everything except the ventral sac, which was obviously broken off in the figured specimen. 

 1 adopt the name nncurvatus» in preference to »granulatus?. because the figured specimen 

 of the former speeies is preserved, and there are many other specimens Rearing the name 

 that must have served as typés to Axgelin. The specimens are fragmentary, Rut the 

 scattered evidence enables one to Ruild up a fairly complete description of the speeies. 



The speeies is transferred to Gissocrinus, notwithstanding the fäet that the number 

 of infrabasals is uncertain, for the following reasons. In the shape and strueture of ils 

 arm-ossicles it resembles many speeies of Gissocrinus, but none of Cyathocrinus; the 

 strueture of the ventral sac is ver} 7 characteristic of, though not absolutely contined to, 

 Gissocrinus; the horizontal position of the ventral sac and of the proximal region of the 

 arms is parallelled by Gissocrinus squanrifer and G. arthriticus, not to mention other 

 speeies more doubtfully referred to Gissocrinus. 



I ani not sure that I appreciate the reasons that eaused Messrs. Wachsmuth and 

 Springer to refer Cyathocrinus granulatus, and by implication C. incurvatus, t<> Arachno- 

 crinus. If, however, the forms grouped under Arachnocrinus are really of this nature. 

 then that genus must be regarded with considerable suspicion. The present speeies un- 

 doubtedly belongs to tho same section of Gissocrini as G. squanrifer, while another English 

 speeies tliat has been regarded ns an Arachnocrinus by various authorities is only a further 

 developmenl in the same direction. But between G. squanrifer and G. goniodactylus there 



