FROM THE UPPER GREENSAND. 285 



EcHiNOSPATAGUs Reneviebi, Wright, iiov. sp. PL LXXV, fig. 1. 



Diagnosis. — Test cordate, much inclined and depressed, the antero-posterior equalling 

 the transverse diameter ; ambulacral pairs petaloidal, unequal in length and structure, 

 and lodged in slight depressions. Anterior pair much flexed ; poriferous zones nearly 

 equal, the inner a little narrower than the outer row ; posterior pair short, curved ; zones 

 equal. Ambulacrum wide, lodged in a deep depression. Test elevated in posterior half 

 and tapering behind to a point ; anterior half sloping rapidly to anterior border ; base 

 flat. 



Dimensions. — Length 1 inch and 4 tenths ; transverse diameter 1 inch and 4 tenths ; 

 height 8 tenths of an inch. 



Description. — This Urchin was catalogued by the late Dr. Eitton as Holaster 

 -complanatus in his lists of fossils from the inferior beds of Lower Greensand exposed at 

 Atherfield, Isle of Wight. A careful examination of all our Neocomian Echinides, 

 however, has proved that, although H. complanatus forms a leading fossil in the Lower 

 Neocomian strata of France and Switzerland, it has never yet been found in England. 

 I have searched carefully most of the public and private collections to find an English 

 specimen, but hitherto without success. Any so-called examples that I have found in 

 the cabinets of my friends were in reality foreign specimens purchased from dealers. 



The outline of E. Benevieri is peculiar, it being as broad as it is long, and 

 terminating behind in a pointed process. This character at a glance distinguishes it ; 

 but when added to others which I shall now point out it renders the difference wider at 

 ■each step of the demonstration. 



The ambulacral pairs are petaloidal and lodged in depressions, whereas in H. 

 complanatus they are superficial. The anterior pair are gently flexed, and the poriferous 

 ^ones are nearly of the same width ; the posterior pair are short and curve inwards, and 

 have equal-sized poriferous zones. The ambulacrum is lodged in a wide anteal sulcus, 

 which is deeper above than at the border. The poriferous zones consist of equal-sized 

 holes placed in oblique pairs. 



The apical disc is small, and the ambulacral summit excentral ; it is much nearer the 

 posterior than the anterior border, and the highest point in the test is on an elevation 

 immediately behind the apical disc. The posterior third of the upper surface is 

 considerably elevated, and the two anterior thirds slope gradually to the border, which 

 imparts a marked character to the test. 



The posterior border is narrow and obliquely truncated downwards and inwards. It 

 is unfortunately covered up with a very hard matrix, which cannot be removed without 

 risk to the specimen. 



