Fauiun — Seventh Rej)ort on the Fishes of the Irish A tlantic Slope. 1 23 



specimens the caudal scales are almost circular. On either side of both tlie 

 dorsal and anal fins a ridge is formed of modified, saddle-shaped scales, each 

 with a large central backwards-directed compressed spine, which is usually 

 crenulated or cut into smaller teeth. This ridge is continued backwards for a 

 variable distance until it merges in the general scale-covering of the body. 

 The precise point at which it ceases to be differentiated is not easy to deter- 

 mine, but, for the dorsal ridge, it lies between 1 ryL and 1^- times the length of 

 the head behind tlie commencement of the first dorsal fin. The dorsal ridges 

 are continued forwards, slightly diverging, to the head. In small specimens 

 of about 24 cms. the crenulation of the spines of the ridges is very slight and 

 is only found on a few scales, but it increases with age, and, in addition, 

 subsidiary spines are developed on each side of the median one. The ventral 

 ridges are similar to those beside the dorsal fin except that their teeth are 

 more depressed and that they are continued backwards for a greater distance, 

 at least 1^ times the length of the head, behind the anus, and possibly 

 further, as in all the Ilelga specimens the caudal region was bare of scales. 

 The ventral ridges are not continued forwards in front of the anus, the whole 

 underside of the body in front of the anus being covered with uniform spinose 

 scales. : : 



Fin rays: 1st dorsal, I + (10-11).; Pectoral, '20-22 ; Ventral, 7. ■ 



First dorsal spine rather less than half as long as the succeeding ray. 



The first dorsal fin is about equal in height to the longitudinal diameter 

 of the eye. The second dorsal is slightly lower than the first and is separated 

 from it by a space equal to the distance between two fin rays. The anal fin 

 is considerably lower than the second dorsal, not more than the vertical 

 diameter of the eye in height. The pectoral arises under the beginning of 

 the first dorsal and reaches back to the level of the commencement of the 

 second dorsal. The ventral arises slightly in advance of the pectoral. Its 

 outermost ray is elongate and reaches about half way to the anus. 



Colour, uniform grey, with interior of mouth and branchial cavity black. 



Measurements of five Helga specimens : — 



(a) (6) (c) {d) (e) 





cm. 



cm. 



cm. 



cm. 



cm. 



Total length, 



24-0 



25-2 



34.5 



38-7 



49-0 



Length of head, 



6-4 



6-5 



9-2 



lO-O 



13-5 



Length of snout, 



2-e 



2-8 



4-1 



41 



5-4 



Diameter of eye, vertical, 



11 



1-2 



1-5 



lo 



no 



Diameter of eye, horizontal, ... 



IS 



1-S 



20 



2-8 



3o 



Inter-orbital space (least), 



1-4 



1-4 



2.2 



2-5 



3-2 



Width of head, 



2-9 



2-7 



4-5 



4-S 



G (i 



Snout to 1st dorsal fin, 



6-3 



(i-9 



10-0 



11-6 



14-4 



Snout to vent, 



91 



9-7 



13-5 



. 15-8 



20-5 



Snout to front of mouth, 



2-5 



2-6 



3-6 



41 



5-0 



E.I.A. PROC, VOL. XSXVI, SECT. B. [R] 



