244 B 



superior angular border sends off' a large fan-shaped osseous plate inward, 

 upward, and forward. Its expanded distal end is doubtless in contact with the 

 clavicle or epiclavicle ; it rises from the scapula without sutural interruption. 

 A shorter, fan-shaped process rises from the lower posterior border of the 

 scapula, and unites by its broad extremity with the inner side of the clavicle, 

 from which it is distinguished by a suture. It incloses a large foramen with 

 the clavicle, and probably represents the coracoid, although I cannot detect 

 any suture separating it from the scapula. It is much shorter than that of 

 Portheus. The postero-external side of the scapula has three articular facets 

 at the outer or thick extremity, from the base of which a wide, deep groove 

 extends inwards to the apex of the bone. Two of the facets are on the plane 



Fig. 10. 



Fig. 10.— Left pectoral spine of Pelecopterus chirurgua, oue-lmlf natural size : a ami b, the opposite 

 anterior basilars; c, crcscentic cotyli for the posterior median basilars; <f cf, three median basilars; sc, 

 scapula ; co, coracoid. 



of the posterior face, one above and one below. The third is between and 

 exterior to them, and stands on an elevated tuberosity. The three together 

 support the pectoral spine. Their surfaces were doubtless furnished with a 

 thick cap of articular cartilage, as they are granular-rugose. The groove 

 above mentioned is divided into five or six transverse subcrescentic fossae, or 

 cotyli, for the posterior basilar bones, whose fundus are also rugose. 



The entire pectoral fin, so far as it is known, is devoted to the construc- 

 tion of a powerful spine. This follows from I he fact that the spine is sup- 



