from the Island of Malta. 97 



shaped as that species; the single ambulacrum is larger and 

 \vider, and the antero-lateral pair are more developed in the 

 (Jri-man than in the Maltese form; they resemble each other 

 in the interambulacrum in both possessing a tail-like terminal 

 process, and in having the posterior border obliquely scooped 

 out ; they are both, likewise, Miocene Urchins, S. acuminatus 

 being found in that terrain near Cassel and Dusseldorf (Ger- 

 many), and at Bordeaux and Blaye (France). 



Affinities and differences. The depth and length of the am- 

 bulacral areas, with the great declivity of the anterior side of the 

 test, and the post-discal carina, with its caudate-like process, 

 serve to distinguish this species from H. Scilla. 



Locality and stratiyraphical position. Collected from bed 

 No. 4, the calcareous sandstone at Malta. We dedicate this 

 species to our friend M. Cottcau, the learned author of ' Etudes 

 sur les lichinides Fossiles du departernent de P Yonne/ who has 

 most generously aided us in our studies, by contributing the 

 types of many of his species to our cabinet for comparative in- 

 vestigations. 



Hemiaster Scilla, Wright, n. sp. PL VII. fig. 1 a-f. 



SYN. Spatangus crassissimus, Desmoulins, Etudes sur les Echinides, 



p. 391. no. 30. 

 Echinus, Scilla, Corp. Mar. pi. 10. fig. 4. 



Test globular, higher behind than before; ambulacral areas 

 short ; single ambulacrum the longest, forming a deep sulcus 

 on the anterior border ; antero-laterals wide, diverging at an 

 angle of 44 ; postero-laterals not half the length of the ante- 

 riors, forming an angle of 56 ; both pairs form sulci on the 

 sides of the test : posterior border squarely truncated down- 

 wards and outwards : the anus high near the dorsum : base 

 convex : mouth at the anterior third, with a large projecting 

 under lip. 



Dimensions. Antero-posterior diameter 1 2 9 ^ inch, transverse 

 diameter l/^ inch, height 1^ inch. 



Description. Much confusion has arisen as to the identity of 

 this Urchin, occasioned probably by the circumstance of Scilla 

 having figured only the base of the test, and neglected to m\< 

 either its profile or the dorsal surface. In M. Agassiz's ' Pro- 

 dromus' it was entered as Micraster Goldfussii, but has been 

 omitted from Agassiz and Desor's ' Catalogue raisonneV M. 

 Desmoulins identifies it with the Spatangus crassissimus of 

 Defrance, but on referring to the original description * of that 

 species, we find that Defrance's species came from " la craie 



* Diet. Sc. Nat. torn. 50. p. 96. 



