270 Dr. T. Wright on Fossil Echiiioderms 



differeuces are found to be still greater : in C. Reidii the test is 

 broader in proportion to its length ; the petaloid ambulacra are 

 narrower ; the poriferous zones are not so open at the base. The 

 apical disc is convex and prominent in C. Reidii, and depressed 

 in C. altus. In C. Reidii the border is thin and sharp, and the 

 base is flat. In C. alius the border is thick and rounded, and 

 the base is concave. In C. Reidii the mouth is small, and the 

 oral lobes curve acutely inwards; whilst in C. altus the large 

 mouth lies at the bottom of a concave depression formed by the 

 gradual inward sloping of the interambulacra. The distinctions 

 between our species and that of C. scutellatus and C. marginatus 

 are so well defined, that it is unnecessary to make a comparison 

 w^ith them. 



Locality and stratigraphical position. — This species is appa- 

 rently from bed No. 1, the Gozo marble, but this we cannot with 

 certainty state. Fine specimens are in the Jermyn Street Mu- 

 seum, and in the collection of the Geological Society of London. 

 We dedicate this species to his Excellency Sir William Reid, 

 Governor of Malta, whose laudable efforts to form a public col- 

 lection of Maltese fossils have greatly contributed to our know- 

 ledge of the palaeontology of the island. 



Genus Pygorhvxchus, Agassiz, 1839. 



In the dismemberment of the genus Nucleolites of Lamarck, 

 M. Agassiz has not been so fortunate as in other groups of 

 Echinida : the characters on which, for example, Catopygus and 

 Pygorhynchus are distinguished from Nucleolites are not satis- 

 factory, as they undergo important modifications in the different 

 species grouped together in each of these new genera. If we 

 take a type specimen of each genus only and compare them 

 together, we admit the distinctions pointed out ; but when we 

 examine several species of each of these genera, we observe the 

 characters gradually blending into the primary type form : as 

 representatives in time, the grouping is valuable, but the zoolo- 

 gical characters in our judgment are too indefinite to found 

 genera thereon. With these remarks we refer provisionally the 

 small Nucleolite before us to the section Pygorhynchus, which 

 is thus characterized by Agassiz : — " Form elongated ; ambu- 

 lacra distinctly petaloid, often costated as in Echinolampas. 

 Mouth central or subceutral, pentagonal, surrounded with five 

 lai'ge lobes, and a distinct rosette of buccal pores. Anus pos- 

 terior, nearer the superior than the inferior border." All the 

 species of the genus Pygorhynchus belong to the nummulitic 

 and tertiary rocks ; those of the genus Catopygus, with one ex- 

 ception, are cretaceous foi-ms. 



