26 ECHINODERMS OF THE LONDON CLAY. 



dimensions of the H. Bowerbankii. The dorsal ambulacra are conspicuously petaloid, 

 and all lodged in shallow depressions. The anterolaterals are rather less than twice as 

 long as the postero-laterals. The latter are ovate, with truncate extremities, and have 

 from twenty to twenty-four pairs of pores in each row. The anterolaterals have about 

 thirty pairs in a row. These numbers refer to full-grown examples. Younger ones have 

 fewer pores. The plates are covered by squamose elevations, bearing nearly uniform 

 tubercular bosses. The peripetal fasciole is rather broad, and but very slightly undulated. 

 The odd ambulacrum is studded with minute granules. 



I have not seen the under side of this species ; nor, though the test is partially well 

 preserved in two instances, is the anal extremity in such a state as to enable me to say 

 with certainty whether there may not be a caudal fasciole. In such case the species must 

 be referred to Brissus. 



There are two varieties, which may eventually prove to be distinct species. The one is 

 from Barton (Mr. Bowerbank), and the other from Haverstock Hill (Mr. Edwards). The 

 former is represented in Plate III, figs. 8, a, b, and c, and the latter in fig. 8, d. 



Genus — Eupatagus, Agassiz. 



More orless ovate and sub-depressed urchins, often of considerable dimensions, with 

 heterogeneous ambulacra distinctly petaloid or subpetaloid in their dorsal portions. The 

 odd ambulacrum is lodged in a more or less deep furrow. The dorsal petals are circum- 

 scribed by a distinct fasciole, and there is another well-marked sub-anal or caudal fasciole. 

 The dorsal plates within the peripetal fasciole bear, besides the ordinary tubercles, large 

 primary ones, in the manner of Spatangus. The mouth is excentric and bilabiate, the 

 vent terminal. 



The species of this genus at present known are either living, or from Eocene strata. 

 The existing forms inhabit the Australian seas. No fossil belonging to it has hitherto been 

 observed in Britain. 



1. Eupatagus Hastingle. Plate III, fig. 7. 



The body of this remarkable and elegant sea-urchin is regularly ovate, and, though 

 much compressed in the specimens, must have been gently convex. The ambulacra are 

 petaloid, with long petals of lanceolate shape, and of equal lengths. Of the lateral 

 ambulacra the two anterior stand nearly at right angles to the axis of the test, the two 

 posterior form an acute angle. The odd one is nearly parallel-sided. None of them are 

 lodged in sulci, but all at the surface of the test. There are about twenty-four pairs of 

 pores in each row on the lateral petals. The petals are circumscribed by a narrow, very 

 distinct fasciole, not sinuated at the sides. The plates are covered with scattered granules 



