714 MR. H. L. HAWKINS ON [Jlllie 15, 



4. An Abnormal Individual o£ the Echinoid Amhlypneiistes. 

 By H. L. Hawkins, B.Sc, Mark Stirrup Scholar in 

 the University of Manchester*. 



[Received June 2nd, 1909.] 



(Text-figures 226-230.) 



A series of the recent Echinoid Amhlypneustes from Australian 

 waters, preserved in the Manchester Museum, includes an in- 

 dividual, apparently of A. ovum, with a particularly fundamental 

 abnormality, which seems worthy of brief description. 



Abnormalities in the symmetry of species of Amhlypneiistes 

 were described in 1880 by F. J. Bell and C. Stewart in the Journal 

 of the Linntean Society (vol. xv. pp. 126 & 130, pi. v.), and it would 

 appear that the genus is one the members of which are especially 

 liable to irregularities of development. The structural peculiarities 

 of my specimen, however, are of a type distinct from those described 

 in the papers refeiTed to, and resemble those in the Echinus 

 esculentus figured bv Messrs. J. Ritchie and D. 0. Mcintosh in the 

 Proceedings of the Zoological Society for 1908 (p. 646, pi. xxxiii.). 



Text-fig. 226. 



V 



Lateral view of test of an abnormal Amhlypneustes. 



The outward form of the specimen is strikingly irregular. 

 Instead of the regular ovoid shape of other specimens of 

 the species, it is much elongated along a line almost corresponding 

 with the antero-posterior axis. The lateral view (text-fig. 226) 

 shoAvs the test to be abruptly truncated adapically, while the 

 apical system of plates rises boldly above the partly concave 

 slopes of the corona. 



The adapical view (text-fig. 227) shows the remarkable feature 

 that only three ambulacral areas reach the apical system, the two 



* Communicated by P. A. Bathee, F.R.S. 



