90 Messrs. E. W. L. Holt and L. W. Byrne on 



the anterior parts were certainly rougher when first observed 

 than at present, after several journeys between Dublin and 

 the British Museum. 



The shape of the back, dependent on the degree of eleva- 

 tion of the body at the origin of the dorsal fin, will probably 

 be a good character in all but the youngest stages, the genus 

 being divisible into forms in which the profile between eyes 

 and dorsal fin is concave and those in which the profile is 

 either straiglit or slightly convex. The pattern of the inter- 

 orbital area, depending on the relative form and positions of 

 the frontal and prefrontal bones, and the consequent outline 

 of the scale-clad area overlying the ethmoid region, probably 

 also offers a constant character. 



In the development of the dorsal and anal spines, relative 

 to the size of the individual, C. boops is intermediate between 

 C. verrucosum and the other species ; but while this character 

 has no doubt a constant specific value, its application at 

 different phases of growth requires considerable caution, 

 because the length of the spines, relative to that of the 

 individual and of the longest articulated rays in the same fin, 

 no doubt undergoes considerable reduction as the fish increases 

 in size. 



So far as our knowledge at present extends, the species of 

 Cytiosoma may be distinguished as follows : — 



1. Dorsal spines VI, anal III, all compara- 



tively feeble and (in a specimen 200 mm. 

 long -without caudal) much shorter than 

 the longest articulated rays. Dorsal profile 

 from back of head to origin of dorsal fin 

 straight or slightly convex. Tubercles on 

 sides of belly persistent at a length of 

 200 mm. (without caudal). L. 1. ca. 95 . . 1. C verrucosum, Gilch. 



2. Dorsal spines VI-VII, anal III-IV, one or 



more in each fin thickened and produced. 

 Dorsal profile from back of head to origin 

 of dorsal fin more or less concave. 



A. Second, third, and fourth dorsal spines 



(in specimens of 95 and 150 mm, without 

 caudal) moderately stout and produced, 

 but shorter than longest articulated rays 

 of same fin, second or third the longest, 

 the third but little longer than fourth. 

 Tubercles on sides of belly obsolescent 

 at 95 mm., absent at 150 mm. L. 1. ca. 

 100. A conspicuous horizontal I'idge on 

 operculum 2. C. hoops, Gilch. 



B. Second dorsal and first anal spines (in 



specimens of 108 to 200 mm. without 

 caudal) much longer and stouter than 

 others, and as long as succeeding articu- 

 lated rays. {Xeoci/ttus, Gilch.) 



