4o6 



SNODGRASS AND HELLER 



length, and has a shape very similar to that of Valenciennes's figure of 

 Xestirus laticlavius, while others duplicate in every w^ay the type 

 of Xesurus clarionh Gilbert & Starks. These 2 extremes certainly 

 have a very different appearance, but our specimens show a closely 

 graded series of differences from one to the other. Since this is the 

 case we recognize only one species, X. laticlavius by priority. 



The pectoral fin varies much in shape ; in some the posterior margin 

 is almost straight, in others the tip is conspicuously bent backward. 

 The greatest depth of body is generally much in front of the middle, 

 being at the vertical through base of ventrals, or even in front of this 

 in specimens of least depth. In small specimens (23 mm. long) the 

 spines of the lateral caudal plates are proportionally smaller than in 

 adults, the anterior angle not elevated nor produced forward, and the 

 margin serrate. On most of the smaller specimens there are onl}' 

 slight traces of spine-bearing plates in front of caudal peduncle; on 

 the large specimens such plates are lai-ge and prominent ; caudal 

 lunate with median rays the length of the ventrals, the lower lobe 

 often longer than upper. In most specimens the lateral line is dis- 

 tinct, in others of the same size it is entirely lacking. 



Most of the variations described above are not dependent on age, 

 nor has the locality or the season any influence in their production, 

 for we found all extremes in specimens of the same size, taken at the 

 same time at the same island. 



MEASUREMENTS AND FIN RAYS OF XeSUrUS laticlaVlUS. 



lyocality. 



No. Stanford University Museum. 



Length in mm 



Depth 



Head 



Pectora 1 



Ventral 



Number of dorsal spines 



Number of second dorsal rays. 

 Number of anal rajs 



12285 



340 



55 

 27 



24 

 14 

 VIII 

 26 

 23 



12286 



240 



43 



29 



26 



16 

 VIII 



26 



23 



12287 



250 

 50 

 32 

 27 

 15 



VII 



27 



22 



12288 



202 



55 

 30 

 27 

 16 

 VIII 

 26 

 23 



12289 



245 

 55 

 32 

 26 



15 



VIII 



26 



23 



Family BALISTID^. 



138. BALISTES VERRES (Gilbert & Starks). 



Pachynathus capis/raius, Jordan & Evermann, Fishes North and Mid. Amer. 

 II, 1704, 1898. — Jordan & McGrkgor, Rep. U. S. F'ish Comm. for 189I 

 (1899), 280 (Revillagigedo Islands) ; not of Shaw. 



