BY WILLIAM A. HASWELL, M.A., B.SC. 85 



a number of smaller intercalary cartilages towards their extremities ; 

 three of the rays on either side of the articulation between the 

 hyo-mandibular and the hyoidean coalesce at their bases. 



The copulare of the first branchial arch articulates with the 

 hyoid copula ; that of the second arch is united with its fellow by 

 the intermediation Of a small copula ; it is connected externally 

 with both the first and the second arches, as often occurs. The 

 fifth arch has no copular. The basal plates of the first three 

 arches are large and triangular ; the third is bilobed at the apex ; 

 the mesial plates are deeply grooved internally near their proximal 

 ends for the attachment of the strong adductors. The first arch 

 has sixteen rays, the second thirteen ; the third twelve. The 

 fourth basal is confluent with the upper mesial of the fifth, their 

 being no representative of the fifth basal.* The mesials of the 

 fourth arch are deeply grooved for the adductors like those of the 

 preceding three which they resemble in form ; it has twelve rays. 

 The fifth has no muscular grooves ; it has no rays, but presents 

 a strong continuous ridge on its outer surface in a position corres- 

 ponding with that of the rays in the preceding arches. 



The Shoulder-Girdle. 



The mesial portion projects very strongly ventrad, forming a 

 fold, and its front margin is greatly elevated towards the middle. 

 The lateral halves are united by continuous cartilage ; except at 

 the dorsal extremities and the mesial uniting portion, they are 

 strongly impregnated with osseous matter. The whole girdle is 

 very broad, much broader than in Carcharias, slightly contracted 

 near the line of junction, and narrowing slightly towards the 

 dorsal extremity. There is no articular process or surface for the 

 branchial skeleton. The articular surface for the pectoral fin is 

 directed downwards and slightly backwards and outwards ; it is of 

 long, narrow form, constricted in the centre. The arrangement of 

 the nerve apertures is in some respects peculiar, and very different 

 from that to be observed in Carcharias. \ The aperture of 



* A similar arrangement occurs in Raja, RUjiichobatus, Scyllium, and Galeus. 

 Vide Gegenbaur, Untersuchungen, II., i., "Schultergurtel der VVirbelthiere." 



