Nos. IAND2.] ANATOMY OF SCOMBER SCOMBER. 125 



shank by the deep anterior end of the groove that lodges the 

 afferent artery of the arch. This ventral edge forms the base 

 of the triangular articular portion of the element. The summit 

 of the triangle, which lies directly dorsal to it, projects upward 

 and slightly mesially, is usually somewhat rounded, and fits into 

 the triangular depression on the lateral surface of the second basi- 

 branchial. The anterior edge of the triangle is not seen in the 

 figures, being hidden from view by the projecting anterior process 

 of the element. It is presented antero-dorsally, is slightly rounded 

 both longitudinally and transversely, is capped with cartilage, and 

 forms the distal articular surface of the piece. The ventral end 

 of the strip of cartilage that caps this edge forms the anterior end 

 of the true ventral surface of the entire element, and is seen in 

 Fig. 30. It touches, or almost touches, in the mid-ventral line, the 

 corresponding part of the hypobranchial of the opposite side of 

 the head. The pointed anterior process of the element is formed 

 by an anterior prolongation of the superficial layers of the lateral 

 and dorso-lateral surfaces of the piece, and its ventral edge forms 

 a direct prolongation of the lateral bounding edge of the groove 

 on the ventral surface of the element. It is slightly concave inter- 

 nally, and extends forward, nearly parallel to the dorsal part of 

 the lateral surface of the first basibranchial, but separated from it 

 by a certain space. 



Where the triangular portion of the element joins the shank, 

 the mesial edge of the grooved ventral surface of the piece is cut 

 away by a groove which, beginning on the hind end of the mesial 

 surface of the triangular portion, leads backward onto the ventral 

 surface of the shank of the element. It lodges the ventral end of 

 the afferent artery of the arch. 



The proximal end of the element articulates with the cerato- 

 branchial of its arch, and is capped with cartilage. 



The Second Hypobranchial (HB, II) resembles the first ex- 

 cepting that its triangular articular portion is stouter, and that the 

 element has no anterior process projecting beyond its articular 

 edge. The entire anterior edge of this hypobranchial is capped 

 with cartilage, and forms the articular head of the piece. The 

 groove on the ventral surface of the shank of the element lies at 

 a deeper or more dorsal level than the continuation of the groove 



