V. Botryocrinus. 393 



The arrangement of the lower plates of the ventral sac 

 varies in species and slightly even in individuals. The Ventral 

 Sac consists of an unascertained number of longitudinal rows 

 of plates, the lateral edges of which plates are folded as in 

 Thenarocrinus ; there is, however, a median posterior region 

 in which the plates are much less or not at all folded ; at the 

 distal end of the sac also the folding lessens or disappears, 

 and this end is often bent round on itself in a posterior 

 direction. In some cases the foldings are broad, in others 

 fine and deep ; in the latter case the appearance of slits is 

 produced, but slits do not exist. 



The Tegmen apparently consists of a large number of small 

 plates continuous with the covering-plates of the arms ; but 

 the actual arrangement of the ventral surface is yet unknown. 



The Stem, rarely long, is sometimes almost stumpy. 

 Distally it may be round, but proximally a pentagonal shape 

 is usually discernible. The lumen is pentagonal. Radial 

 sutures were probably present in the young at least of all 

 species, but they cannot always be traced in the fossils. 



The ossicles are low and have radiating stria? on the arti- 

 cular surface. 



There were radicular cirri, but no cirri on the stem itself. 



Species of the Genus. 



The species hitherto known are : — 



Botryocrinus ramosissimus, Angelin; 1878, Iconographia, 

 p. 24. Syn. B. corallum, Ang. ibid. Op. cit. tab. xv. 

 ff. 9, 9 a, tab. xx. f. 8, tab. xxiii. if. 14, 15, 16, 16 a, 

 tab. xxiv. f. 4. Silurian,/ ( = Aymestry ?), Gotland. 



Botryocrinus cucurbitaceus, Ang., sp., 1878, olim Sicyocrinus. 

 Iconographia, pp. 23, 24, tab. iv. f. 9, tab. xvi. f. 5. 

 S. Love'n, in H. Trautschold, " Ueber Crinoideen, Zu- 

 satze und Berichtigungen," Bull. Soc. Imp. Nat. Mosc. 

 lvii. pp. 140-145, Moscow, 1882. Silurian, c ( = Wen- 

 lock shale), Gotland. 



Neither of these have yet been found in England ; in their 

 stead are three species not yet described, for which I propose 

 the names Botryocrinus ramosus, B. decadactylus, and B. 

 pinnulatus. 



