308 INFULASTER. 



As I have been able to obtain only fragments of this Urchin, too imperfect for 

 description, I shall transcribe the account which my late esteemed colleague Professor 

 Edward Forbes, F.R.S., gave of it in the ' Memoirs of the Geological Survey ' decade iv, 

 p. 3, 1852. 



" For some time," says Forbes, " I was under the impression that this extraordinary 

 and anomalous little Urchin, of which specimens were kindly communicated by Dr. Bower- 

 bank, Mr. Wetherell, and ]\Ir. Woodward, was the young of the CarcUasfer excenfricus, 

 different as its outline is. The series of specimens of various sizes of the latter shown me 

 by Mr. Rose convinces me that it is necessary to regard this beaked and iVe<?ra-like form 

 of Cardiaster as distinct. All the examples are impressed with the same peculiarities. 

 The number submitted to me has been seven, including fragments ; and in addition to 

 those lent for examination are two fine specimens, one of them nearly entire, found by 

 Mr. Cockburn, in the Chalk-with-Flints, at Bostal Heath, near Plumstead, and generously 

 presented by that gentlemen to the Museum of Practical Geology. 



" The striking feature of this form is the rhomboidal profile which it exhibits in conse- 

 quence of the obliquity of the anteal and posteal truncations, both inclining forwards at 

 considerable angles (fig. 2 a — e). The anteal ambulacral sulcus is very deep, long, and 

 narrow ; it rises obliquely to a great height in consequence of the elevation of the apical 

 disk upon a sort of beak (fig. 2 e). The genital plates are assembled just below its summit, 

 which is notched by the turning over, as it were, of the anteal furrow. The details of 

 the lateral ambulacra, in consequence of their being completely plane and very obscure, 

 can with difficulty be distinguished ; the rostrum bends forward slightly in its upper 

 part. The summit of the back is more or less sharply carinated, and declines rapidly with 

 a faint concave curve, until it terminates in the summit of the very oblique and rapidly 

 declining posterior truncation, in the uppermost part of which, at rather less than the 

 total height of the body, is the anus, placed at one end of a groove. The whole of the 

 dorsal surface of the test is covered with granules interspersed with scattered minute 

 tubercles, which become more numerous on the slightly tumid cheeks. The fasciole is 

 strongly and distinctly marked, and passes from beneath the anus over the cheeks. 

 The base is flattened, and except on the ambulacral spaces is strongly tuberculated. 

 The mouth is very small and far forward." 



Dimensions. — The largest specimen measured in length at the base, eight twelfths of 

 an inch ; in breadth, six twelfths of an inch ; and in height, ten twelfths of an inch at 

 the anteal sulcus. 



Locality and Strati^rapJdcal Position. — In the Chalk-with-Flints of Kent and 

 Norfolk. 



