BRITISH FOSSILS. 



3 



ambulacral space, with an arched curve not so deeply inturned as 

 the lateral curves are. 



"The anal extremity of the test is perpendicularly truncated 

 (a character also distinctive between this species and B. carinatus), 

 the anus lenticular and large, and placed rather low down, and the 

 sub-anal or caudal fasciole broadly obcordate, truncated below. The 

 mouth is transversely semicircular, with a slightly overhanging and 

 prominent lip. The oral ambulacra are sub triangular. The tubercles 

 of the post-oral spinous region aresubequal and radiating, and closer 

 set than on the lateral spaces, or in front of the mouth.'' 



Locality. — Coralline Crag, Iken, Ramsholt, and Sudbourn, in 

 Suffolk. (Mus. Pract. Geology, British Museum, &c.) 



Foreign Localities. — Miocene, Malta (Prof. Forbes). (Mus. 

 Pract. Geology.) 



Explanation of the Plate. 



Fig. I. Brissus Scillce, Ag., from Iken (Mus. Pract. Geology). 

 Fig. 2. Side view of do. 



Fig. 3. End view, showing the anal opening and sub- caudal fasciole. 



Fig. 4. Lateral view of another specimen, the vertex placed more anteriorly. 



Fig. 5. Under view of recent specimen, to show the plates of the mouth. 



Fig. 6. Genital openings and ocular plates, Avith the madreporic plate occupying the 



place of the fifth genital pore. 

 Fig. 7. Portion of peripetal fasciole, magnified. 

 Fig. 8,. Tubercles and granules, magnified. 

 Fig. 9. Ambulacral pores, magnified. 

 Fig. 10-13. Spines more or less magnified. 



Fig. 10. Is a lateral view, and 11, a front view of a spine with a spatulate tip. 



March 1856. 



E. Forbes (1852). 



