432 GRACE A. WELLS 



broad plate bearing two processes, one extending laterally on 

 the postero-dorsal edge, and the other projecting on the antero- 

 ventral margin; these are for articulation with the ceratohyal. 



The five brancial arches are all very similar in structure, 

 each half arch consisting of four pieces of cartilage, so con- 

 nected with the ether half as to form a hoop-like support (in- 

 complete dorsally) for the pharnygeal region. The most dorsal 

 element of each arch is the pharyugobranchial cartilage (ph.br.) 

 a flattened, pointed plate with its free inner end extending in- 

 wards and backwards beneath the vertebral column, The 

 fourth and fifth pharyngobranchials are united at their distal 

 ends, and there are longitudinal grooves on the dorsal basal 

 ends of the second, third and fourth of these elements, which 

 are for the passage of blood vessels (b.) to the gill folds. (In 

 one specimen the grooves terminated in a foramen in the fourth 

 and fifth pharyngobranchial of one side). 



At its ventral end each pharyngobranchial articulates with a 

 short epibranchial (e.br.) bearing gill rays on its posterior border. 

 These elements are flattened and each has its dorsal end ex- 

 panded where it articulates with the pharnygobranchial. 



Ventrally the epibranchials are succeeded by the longer cerato- 

 branchials (c.br.), each bearing similar gill rays. At their medial 

 or ventral ends the five pairs of ceratobranchials articulate 

 with each other, and the four anterior are connected medially 

 with three pairs of short hypobranchials (hy.br.) the relations 

 of these latter being as follows : 



The anterior pair of hypobranchials are connected with the 

 first pair of ceratobranchials. They bend inwards and back- 

 wards below the pharnyx and meet in the middle line. Pos- 

 teriorly they articulate with a median plate of cartilage, the 

 first basibranchial (b.br. 1 ). The second pair of hypobranchials 

 are related in a similar way to the second ceratobranchials and 

 meet each other in the median line, while the first basibranchial 

 is included between their anterior margins. Posteriorly they 

 abut against the second basibranchial to be described in a 

 moment. The third pair of hypobranchials articulate laterally 

 with the third and fourth ceratobranchials, while medially they 



