196 ME. P. H. CARPENTER ON THE GENUS SOLANOCRINTTS 



ance ; and nearly the whole of the great dorsal fossa is visible 

 in a view of the calyx from above. The central pit in this fossa 

 is rather less conspicuous than usual. The dorsal surface of the 

 radial pentagon (fig. 9 b) is singularly like that of A. costata and 

 of the closely related (if not identical) A. Gresslyi, Efcallon. 

 There are five rod-like basals, which are barely in contact cen- 

 trally, while their outer ends are just traceable on the exterior of 

 the calyx (PI. IX. fig. 9 a). 



Diameter 12 millims. ; height 4 millims. 



This species has some resemblance to A. JPicteti, de Loriol, 

 but is more than twice its size, and is from the Middle Jurassic 

 rocks, whereas A. Picteti is from the Neocomian. 



YI. — We now come to a type which has given rise to a good deal 

 of discussion. Among Goldfuss's figures of Solanocrinus costatus 

 (tab. 1. fig. 7) there is one (fig. 1c) which does not agree at all 

 either with the other figures or with Goldfuss's text. There are 

 no external basals, and the radials have no outer surfaces, their 

 articular faces rising directly off the eeutrodorsal, very much as in 

 Quenstedt's specimen represented in Pl.IX.fig. 5. But Goldfuss's 

 specimen had no external basals, which are present in the original 

 of fig. 5. Goldfuss does not seem to have noticed that it scarcely 

 agreed with his definition of Solanocrinus ; but the peculiarity 

 was observed by d'Orbigny *, who supposed that the radials were 

 absent as well as the basals, as he mistook their articular faces 

 for a part of the eeutrodorsal. It is difficult to understand this 

 error, as the resemblance of the five articular surfaces to those 

 of the radials of S. costatus would almost seem to have been a 

 sufficient guide. It is interesting, however, as showing how com- 

 plete was the ankylosis of the radials and eeutrodorsal. 



On this specimen d'Orbigny founded a new genus, ComatuUna, 

 which he defined as follows : — 



" Ce sont des Comatules oil il manque a la fois au calice les 

 pieces brachiales et basales, ou les bras s'articulent immediatement 

 sans intermediaires a la piece centrale pourvue de rainules." 



On this subject Pictet remarks : — " M. d'Orbigny a etabli un 

 genre ComatuUna pour des calices dans lesquels les pieces basales 

 et les radiales manqueraient, et les bras s'articuleraient directe- 

 ment a la centrale. Cette description semblerait indiquer un 

 genre bien tranche ; mais M. d'Orbigny prend pour type le 

 S. costatus, Goldf, qui a evidemment des petites pieces basale3." 

 * Op. (At. ii. (i.) p. 139. 



