BY WILLIAM A. HASWELL, M.A., B.SC. 99 



open groove. The post-orbital processes are not conspicuous. The 

 palato-basal articulation is placed far back on a level with the 

 hinder boundary of the orbit. The rostrum is formed of a mesial 

 and two lateral parts ; the former being a prolongation of the 

 roof and floor of the cranium, and containing a canal continuous 

 with the cranial cavity and running forwards to the end of the 

 snout. The lateral parts are continuous behind with the cartilage 

 of the olfactory capsules ; they form thin plates bordering the 

 mesial part and perforated by numerous apertures. The hyoid 

 arch, as in Sharks generally, articulates above with the distal 

 extremity of the hyo-mandibular ; ventrally it unites with a 

 copula which has the form of a very narrow curved bar. Both 

 the hyo-mandibular and the hyoid cartilages are provided with rays. 



The hyoid copula is represented by a transverse band. There is 

 a common branchial copula without any trace of transverse 

 division. The first branchial arch is connected not with this, 

 but with the hyoid copula The second, third, and fourth arches 

 have well-developed copularia, which decrease in size from before 

 backwards. The muscular excavations on the first four arches are 

 perforated by foramina. The external branchial arches are 

 represented by slender cartilages. 



Pectoral and Pelvic Fins. (Plate I., figs. 11 and 12.) 



In the pectoral arch the hinge- like central portion found in other 

 Sharks is not well marked, the two halves being capable of very 

 little motion upon one another. As in the Sharks generally the 

 dorsal ends of the arch are wide apart from one another and have 

 no articulation with the spinal column. The propterygium is only 

 represented by a slender, ray-like cartilage ; the mesopterygium and 

 metapterygium on the other hand are well- developed, and contribute 

 nearly equal shares to the support of the rays ; the metapterygium 

 bears at its extremity a polygonal accessory cartilage with which 

 a few short irregular i-ays articulate.* There is nothing in the 



* In the general arrangement of the cartilages there 19 a close resemblance to P.japonicus, 

 as described and figured by Mivart (1. c, p. 453., pi. LXVIII., fig, 1.) 



