16 



" The mouth is central. The vent none. 



" The cavity is simple. 



" The parietes are thin and minutely dotted, and the centre of 

 the dorsal disc is pellucid. 



" This genus is very nearly allied to the fossil described by Dr. 

 Goldfuss in his beautiful work on Petrifactions, under the name ot 

 Glenotremites paradoxus (tab. iQ. f. 9. and t. 51. f. 1.), with which it 

 agrees in external appearance and form, in the possession of 

 a sunken space on its upper surface, and in having only a single in- 

 ferior pentagonal mouth. It differs from Glenotremites by being un- 

 furnished with ambulacra running from the angle of the mouth to 

 the margin, by being unprovided with conical cavities between those 

 near the mouth, and by having in the flattened disc on the back a 

 central quadrangular impression instead of the pentagonal star of 

 that genus. 



*' Dr. Goldfuss describes the glenoid cavities on the surface as 

 giving attachment to spines similar to those of the Turban Echini, 

 (CzWffm, Lam.), and states that the under surface is covered with very 

 small tubercles to which he believes spines were attached. The 

 cavities on the surface of Ganymeda and the pits in them have very 

 much the form of those figured by Dr. Goldfuss in his fossil, but I 

 cannot regard them as being fitted for the attachment of spines: 

 they have much more resemblance to the mouths of cells. So great, 

 indeed, is this resemblance, that I entertained doubts whether the 

 whole mass might not be a congeries of cells like the Lumilites, 

 rather than the case of a single body, until I considered that it was 

 impossible, from its form, that it could increase in size with the 

 growth of the animal, and that its exceeding regularity proved that 

 it must be the formation of a single creature. 



" I am induced to consider these two genera, though differing in 

 the above-stated particulars, as forming a family or order between 

 the Echinida and the Asteriida; allied to the latter in having only 

 a single opening to the digestive canal, and agreeing with the former 

 in form and consistence, but differing from it in not being composed 

 of many plates. 



" I only know two specimens of this genus, which I believe were 

 found on the coast of Kent, as I discovered them mixed with a quan- 

 tity of Discopora Patina which I collected several years ago from 

 Jiici and shells on that coast. The specimens are ^ of an inch in 

 diameter. 



"I propose to call the species Gatii/meda pulchella," 



