200 ME. P. H. CAEPEXTEE OX THE GENUS SOLAXOC SINUS 



ofd'Orbigny. Neither of them is identifiable with Quenstedt's 

 " Missbildung " ('Jura,' tab. 88. fig. 11), wbile they are also dif- 

 ferent from one another (PI. X. figs. 10, 11). The larger one, 

 Antedon Tessoni (fig. 10), belongs to the Tesson collection, in 

 which it was received nnder the name of Millericrinus regularis, 

 d'Orb., a somewhat singular name, as d'Orbigny's description* 

 of this species commences " sommet inconnu " ! The specimen in 

 question is from the Argile de Dives (Oxford clay) of Vache Noire, 

 and is therefore older than the Nattheim. Comatulce from the 

 upper beds of the "White Jura. Nevertheless it has a most striking 

 general resemblance to the type of Antedon costata (PL IX. fig. 1 a), 

 except for the radials resting directly on the centrodorsal all round, 

 instead of being cut off from it by basals at the augles. They 

 have a large external surface continuing the upward slope of the 

 centrodorsal, and looking downwards and outwards just as in 

 Ant. costata, while the appearance of the ventral aspect of the 

 calyx is very much the same in both species. Ant. Tessoni is 

 distinguished, however, by the nature of the articular faces of 

 the radials. These have much more distinct ridges, separating 

 the muscular fossae above from the ligament-fossae below, than I 

 have seen in any specimen of Ant. costata ; while the ligament- 

 fossae themselves are separated by a groove, proceeding down- 

 wards from the intermuscular notch and ending round the open- 

 ing of the axial canal. These characters alone are sufficient to 

 indicate the specific distinction of this type. 



Diameter 12 millims. Height 8-| minims. ; radials 4-L minims. 



IX. — The smaller "Decameros'''' in the British Museum is from 

 Nattheim, andits ventral aspect much resembles that of Ant. Tessoni 

 and Ant. costata. But the external surface of the radials (PI. X. 

 fig. 11) is small, and looks almost directly downwards, as in Ant. 

 truncala (PI. IX. fig. 3). Although I fully believe basals to be 

 wanting at all the angles of the calyx, I cannot speak with abso- 

 lute certainty about it ; for there are some suspicious-looking 

 lines at one angle that might be the sutural lines of a small basal. 

 "Were they 30, this species would be brought still nearer to Ant. 

 truncata, from which, however, it differs altogether in the nature 

 of the articular faces. They are higher in proportion to their 

 width, and have well-developed muscle-fossae separated distinctly 

 from the ligament-fossae, a,sinAnt. Tessoni; but the mode of sepa- 

 ration is different. In Ant. Tessoni the fossae are separated by a 

 * ' Orinoi'des,' p. 88 



