INVERTEBRATES. 397 



gradually tapering, and trigonal or subtrigonal, being flat below, 

 angular on each side, and angular or rounded above. * 



Appendages of the under side unknown, excepting one of 

 the legs, which is seen in one specimen, projecting out from 

 under the cephalo-thoracic shield, between its posterior margin 

 and the abdomen. It is slender, and shows of the first seg- 

 ment projecting from under the shield, a length of about 0.12 

 inch. The next segment appears to be 0.25 inch in length, 

 with a breadth of only 0.04 inch. The succeeding segment 

 can be traced in the matrix for a distance of about 0.30 inch, 

 being slightly curved near the extremity, and apparently 

 tapering to a point, but the specimen is not in a condition 

 to show its termination. It is not possible to determine which 

 one of the legs this is. Entire length, from the extremity of 

 the caudal segment to the anterior margin of the cephalo-tho- 

 rax, about 1.90 inches. Length of cephalo-thorax, 0.57 inch; 

 breadth of do. to the extremities of postero-lateral spines, 1.70 

 inches; length of area included within the ocular ridge, 0.50 

 inch; greatest breadth of do. (which is the distance between 

 the eyes), 0.60 inch. Length of abdomen, 0.65 inch; breadth 

 of do., exclusive of the flattened margin, 0.94 inch, including 

 it, 1.06 inches; breadth of mesial lobe, 0.23 inch; length of 

 caudal segment, about 0.60 inch. 



Of the known species of Bellinurus, ours seems to be most nearly related to 

 B. belluhis, Koenig (the type of the genus, if we mistake not), which is 

 regarded as being identical with Limulus rotundatus, of Prestwich, (Trans. 

 Geol. Soc, London, v. p. 491, pi. xli, figs. 4, 6 and 7.) From this species, 

 however, it may be at once distinguished by having the lateral angles of its 

 cephalo-thorax produced into long, slender spines, and the flattened border of 

 ►its abdomen proportionally much narrower, and armed with a series of sharp- 

 curved spines, instead of being merely serrated. 



We should also remark here, that Prof. Owen's figure of B. bellulus (Palse- 

 ontology, p. 42), as well as that given by Murchison of the same, under Prest- 

 wich's name rotundatus (Siluria, p. 281;, represent the eyes as being located 

 at the lateral extremities of a large, transversely oval or subelliptical area; 

 while within this there is a smaller, crown-shaped area, defined by a 



