297 



1^02.j PLECTOGNATHOUS FISHES. 



rough or tessellated. Body truncate posteriorly, without caudal 

 peduncle. Caudal fin absent, the dorsal and anal fins confluent 

 posteriorly. Skeleton moderately ossified. Air-bladder absent. 



Genera. 



1 . MoLA Cuv. — Body ovate, compressed : skin thick, rough. 

 Vertebrae 17. ^ 



2. Ranzania Nardo.— Seems chiefly different from Mola in 

 having the body covered with small hexagonal juxtaposed plates. 



Part II. 



Notes on some Plectognathous Fishes, and Descrijitions of some 

 new species in the British Museum Collection. 



In these descriptions the length of head is measured from the 

 tip of the snout to the upper end of the gill-opening, the depth 

 of body at the level of the vent, the movable pelvis or inflatable 

 belly making the measurement of the greatest depth uncertain. 



Balistes naufragium Jordan & Starks. 



In descriptions of this species a feature of some importance 

 has been overlooked, i. e. that the scales on the cheeks are 

 arranged in parallel horizontal series, with naked lines inter- 

 vennig between those in front of the pectoral, and although 

 closely allied to Balistes capriscus Linn, it is still closer to 

 B. flavimarginatus RlLpp., and should have been placed in the 

 genus Xanthichthys recognized by the authors who named it. 



Incidentally this species demonstrates of what little value are 

 genera based on features so trivial as those supposed to separate 

 Balistes from Xanthichthys. 



Balistes castaneus Richardson. 



This species, described by Richardson in the ' Voyage of the 

 Sulphur, Fishes' (p. 126, pi. 59), has been included by Gunther 

 m the synonymy of Balistes capriscus Linn., from which it differs 

 m many ways, and I therefore take the opportunity of redescribing 

 Richardson's type specimen. 



Depth of body twice in total length, length of head 3 times. 

 Snout 3 times as long as the eye-diameter, which is | of the 

 mterorbital width, which is less than i the length of head and 

 equal to the length of the gill-opening. A groove below the 

 nostrils ; 2 or 3 enlarged plates behind the gill-opening. D. Ill, 

 28. A. 26. The first dorsal spine above the gill-opening, with 

 about 8 vertical rows of minute tubercles anteriorly, somewhat 

 curved, its length 1| times in the length of head; second and 

 third spines prominent ; soft dorsal somewhat elevated anteriorly, 

 the fifth ray the longest, longer than the first dorsal spine. Anal 

 similar, but not so deep. Caudal truncate, with the outer rays 

 slightly produced. Scales on the cheeks in oblique series without 

 naked lines intervening, on the caudal peduncle not bearing 



