As a result of the observation of the above specimens it appears that the greatest annount 

 of individual variation is found in the shape of the cranium, so that it would be difficult to recog- 

 nize any basic form for it. In the case of the vertebrae and the so-called membrane bones, 

 although there was more or less individual variation, the basic forms were comparatively clear 

 and they were convenient for carrying out comparisons among the species. 



1. 



External form 



(a) General appearance 



The most conspicuous characteristic of the spearfishes is a sword or spearshaped upper 

 jaw formed by the prolongation of the premaxillary, maxillary, and nasal bones. The principal 

 bones making up the elongated upper jaw are the premaxillary and the nasals, the maxillary 

 itself attaining only one-half the length of the upper jaw as a whole. 



In the broadbill swordfish the snout is conspicuously flattened and broad, having the shape 

 of a double-edged sword, but in the Istiophoridae it has the form of an elongated cone with a 

 roughly circular cross section. The note of Jordan and EvermannJ_5.'in regard to this point, 

 "upper jaw prolonged into a spear or sword which is shorter and narrower and more flattened 

 on the edge than in the true swordfish or broadbill" can hardly be thought to be based on complete 

 observations. 



Generally the bodies of the spearfishes other than the broadbill are markedly longer and 

 at the same time more laterally compressed than those of the sconnbroid fishes, which are con- 

 sidered to be most closely related to them. In the Istiophoridae generally, in differing degrees 

 the outline of the dorsal surface projects conspicuously anterior to the origin of the first dorsal 

 fin, with a gradual slope posteriorly from this part to the caudal peduncle. The ventral profile 

 is somewhat swelled out in the vicinity of the base of the ventrals but to a far less conspicuous 

 degree than in the case of the dorsal projection. 



The greatest body depth is measured between the origin of the ventrals and between the 

 third spine and the second soft ray of the first dorsal, the line passing just through the posterior 

 end of the base of the pectoral fins. If the head is cut off on this line, the rest of the body forms 

 an almost regular trapezoid, although the bases of the second anal and the second dorsal project 

 somewhat. The trunk is more or less compressed laterally and the caudal portion is roughly 

 round, the cross section through the caudal peduncle being circular. The degree of lateral com- 

 pression is most striking in the shortnosed spearfish, followed by the sailfish, and is least con- 

 spicuous in the black marlin. In the broadbill, except for the snout, the body of the fish is a 

 well proportioned spindle shape, the trunk is short, and the projection on the dorsal profile is 

 far less conspicuous than in the case of the istiophorids. The istiophorids have two pairs of 

 keels on the caudal peduncle, while the broadbill has a single pair of very large ones. 



Among the istiophorid fishes the body depth is greatest in the white marlin and least in 

 the shortnosed spearfish, there being quite striking differences among the species in the 



10/ 



— Jordan and Evermann. Occ. Papers, Calif. Acad. Sci. , XII, 1926. 



