1 62 ALUS. [Vol. XVIII. 



Ventral to the fenestra, the procoracoid, which here alone articu- 

 lates with the clavicle, is not so lined, excepting only at the extreme 

 ventral tip of the bone which ends in a small bit of cartilage. 

 Dorsal to the fenestra the scapulare and procoracoid articulate with 

 the inner, or mesial surface of the mesial plate of the clavicle ; ven- 

 tral to the fenestra the procoracoid articulates with the outer, or 

 lateral surface of the same plate. 



The dorso-posterior edge of the united scapulare and procor- 

 acoid has a long rectangular piece cut out of it, the cut being con- 

 siderably deeper at its ventro-posterior than at its dorso-anterior 

 end. In the space thus cut out of the scapulare and procoracoid 

 lie the four basal bones, their free dorso-posterior edges lying on 

 a level with the corresponding and adjacent portions of the 

 scapulare and procoracoid. The excision is lined with cartilage 

 its full length, excepting only in that part that lies betweei) 

 the posterior edge of the posterior basal bone and the adjoining 

 edge of the procoracoid. Cartilage also extends outward between 

 the basal bones, and entirely around the anterior basal bone. An- 

 terior to the anterior basal bone the edge of the scapulare is capped 

 for a short distance with cartilage, and, anterior to this cap, the 

 bone is cut away. A part of the edge of the scapulare is thus left 

 which projects as a rectangular eminence and looks like an an- 

 terior continuation of the line of basal bones. In two of the three 

 specimens examined this eminence gave articulation to the three 

 anterior dermal rays of the pectoral fin ; in the third specimen the 

 articulation of the rays was as shown in the accompanying figures. 



The scapulare is pierced by a foramen of variable size and posi- 

 tion which gives passage to the nervus pterygialis and doubtless 

 also to the artery that supplies the fin, though this was not traced. 



The four basal bones are sub-rectangular pieces the adjoining 

 edges of which are cut out in the middle so as to form three small 

 and nearly circular openings. Between the posterior edge of the 

 posterior bone and the adjoining edge of the procoracoid there is 

 a similar but larger and more oval opening. Between the anterior 

 edge of the anterior basal bone and the adjoining process of the 

 scapulare there is no opening. The posterior basal bone lies en- 

 tirely opposite the procoracoid ; the next anterior one lies opposite 

 the cartilaginous line between the procoracoid and scapulare ; and 

 the two anterior ones opposite the scapulare. 



