NATURAL SCIENCES OF PHILADELPHIA. 119 



ACANTHOLATRIS Gill. 



Synonymy. 

 Chaetodon sp. Carmichal. 

 Cheilodactylus sp. Cuv. et Val., &c. 

 Chilodactylus sp. Giinther. 



Caput conicum. Pinna analis o 7 >longa spinis tribus robustis et radiis circa 

 iluodecim paulo decrescentibus. 



Body oblong and subfusiform, higbest above the ventral fins, and with the 

 caudal peduncle slender. Scales moderate or large. Head rather small, 

 conical and with the profile nearly straight. Eyes mostly above the rostro- 

 opercular horizon, and nearly intermediate between the snout and nape. Pre- 

 operculum subvertical behind. Mouth smalL Jaws nearly equal. Lips thick. 

 Teeth pluriserial in each jaw. Branchiostegal rays six. Dorsal fin with its 

 spinous portion rather longer than the soft, arched and with about seventeen 

 stout spines, as high or higher than the soft dorsal. Anal fin oblong, with 

 three robust spines and twelve rays which very slowly diminish in length. 

 Pectoral fin with a simple ray considerably produced. 



Type. Acantholatris monodactylus Gill. 



This genus is distinguished by the nearly uniform height of the anal, the 

 strong spines of the dorsal and anal and the conical head. It appears to be 

 most nearly allied to Chirodactylus and Chilodactylus, but differs especially 

 from the first in the development of the anal fin and the strength of the spines, 

 and from the second by the larger scales and the presence of six branchioste- 

 gal rays. 



The only species of the genus that is well known is the one described by 

 Carmichal in his treatise on the Fishes of Tristan d'Acunha. 



Acantholatris monodactylus Gill. 



Chaetodon monodactylus Carmichal, Transactions of the Linnsean Society, 



vol. xii. p, 300, pi. 21. 

 Cheilodactylus Carmichselis Cuv. et Val., Hist. Nat. des Poissons, tome v. 



p. 360 ; ib. tome ix. p. 489. 

 Cheilodactylus Carmichselis Cuv. Regne Animal, ed. ill., Poissons, pi. 31, 



fig- 2. 

 Chilodactylus monodactylus Giinther, Catalogue of the Acanthopterygian 



Fishes, &c, vol. ii. p. 81. 

 Hab. Coast of Chili. 



CHIRODACTYLUS Gill. 



Synonymy. 

 Chilodactylus auct. 



Caput conicum. Pinna analis ad angulum anticum multo producta, spinis 

 tribus et radiis 7 10. 



Body highest above the ventral fins, declining quite rapidly towards the 

 slender caudal peduncle. Scales of moderate size. Head rather small, much 

 compressed, presenting in profile a conical appearance, with the profile oblique 

 and nearly straight. Eyes on or just above the rostro-opercular line, and 

 mostly anterior. Cheeks and crown scaly. Preoperculum extended below, 

 with the posterior margin vertical. Mouth small. Lower jaw shorter than 

 the upper. Lips well developed. Teeth on each of the jaws pluriserial in 

 front. Branchiostegal rays (J 6. Dorsal fin with its spinous and soft por- 

 tions nearly equally long. The former is convex and highest near the middle, 

 and much lower behind than the soft part. Anal fin short, with its three 

 spines moderately produced at its anterior angle and rapidly diminishing be- 

 hind, so that the rayed margin is nearly vertical. Pectoral fins with one of 

 the simply articulated rays moderately produced. 



1862.] 



