486 J. W. Gregory — Australian Echinoidea. 



fascioles cannot now be recognized ; but in his discussion of the 

 question Prof. Duncan emphasizes the fact that the specimen is 

 certainly specifically distinct — quite apart from the fascioles — from 

 any described species of Pericosmus. Prof. M'Coy, on the other 

 hand, regarded it as probably identical with his P. compressus, 

 though he noted that in addition to the fascioles the latter has a 

 convexity, instead of a concavity, near the summit of the unpaired 

 interradius. 



In Mr. H. P. Woodward's collection there is a Pericosmus which 

 agrees in the character noted by Prof. M'Coy, and in other points 

 with Dr. Duncan's specimen. After a comparison of this with the 

 specimen of Megalaster, I entertain no doubt that the two are 

 specifically identical, and that consequently Megalaster must be 

 abandoned. 



As to the second question, whether Pericosmus compressus, Dune, 

 sp., is the same as P. compressus, M'Coy, I agree with Dr. Duncan 

 rather than with Prof. M'Coy and Prof. Hutton. The two species 

 differ in the following points : P. compressus, Dune, sp., is longer 

 than wide, whereas the other is wider than long : in the former 

 the anteal sulcus is wider and shallower; the anus is oval instead 

 of round; the anterior slope is steeper; the test is higher; the apical 

 disc is more anterior; there is a concavity behind the apical disc; 

 the ambulacra are less lanceolate, blunter and sinuous. These form 

 a combination of characters that are quite sufficient to continue the 

 separation of the species. But the absorption of Megalaster in 

 Pericosmus necessitates the adoption of a new name for the later 

 species. I have much pleasure in calling it after Prof. M'Coy, as, 

 owing to his admirable work, his name must always be associated 

 with the species ; its renaming is only required owing to the 

 perspicuity with which Prof. M'Coy interpreted Prof. Duncan's 

 description and outline figure, and to the caution with which he 

 hoped to save palaaontological nomenclature from a useless synonym. 



After Prof. Hutton's : remark, it is perhaps advisable to compare 

 P. M'Coyi with the description of Meoma crawfordi, Hutton. The 

 Australian species differs from the New Zealand one in that (1) it 

 is not a Meoma ; (2) it is broader than long — not longer than broad, 

 as shown by Prof. Hutton's measurements ; (3) the an tero- lateral 

 ambulacra are equal or slightly longer than the postero-lateral. 



II. — Dr. Taylor's Collection. From the banks of the Murray 

 Eiver at Morgan. 2 



Fam. Arbaciimi. 



Gen. Ccelopleurus, Ag., 1840. 



Ccelopleurus paucituberculatus, sp. nov. PI. XIV. Figs. 4 and 5. 



Test tumid ; depressed abactinally ; concave below. Circular. 



1 F. W. Hutton, " On the Correlations of the ' Curiosity- Shop Bed,' in Canterhury, 

 New Zealand," Q J.G.S. 1885, vol. xli. p. 554. 



2 The sections at this point have been fully described by Prof. Tate in his " Notes 

 on the Physical and Geological Features of the Lower Murray Eiver," Trans. 

 Boy. Soc. S. Australia, 1885, vol. vii. p. 35. 



