727 



a 



Total length 49 ram 



Height of hody ... 31 - 

 Length of head .... 14 - 

 A. aculeatiis is distinguished from Â. olfeisii (Cuv.j 1829, princi- 

 I)ally by the following characteristics : 



1) Greater relative height of the body, thi.s being about equal to 

 the distance from the orbit to the root of the tail (in A. olfersii from 

 the gill-cover to the root of the tail). 



2) A number of short, spiny crests along the ventral line of the 

 body (absent in A. olfersii). 



8) A relatively larger eye, its heigt being contamed about 8 times 

 in the total length of the body, and 2,3 times in that of the head (in 

 A. olfersii about 2,8 times). 



The radial formula is: D. 9; A. 7 -+- 5 (as in A. olfersii), but the 

 series is in places interrupted by spines, 2 of which are in front of the 

 8th anal ray, and 1 behind it. 



The spinous armature along the ventral outline of the body con- 

 sists of the following parts: 



a. A toothed ridge on each side of the vent. 



b. A short, fan-shaped ridge, consisting of from 2 to 7 teeth, of 

 wdiich the middle ones are the longest, between the seventh and eighth 

 anal rays. 



c. A single spine between the eighth and ninth anal rays. 



d. A toothed ridge on each side of the ventral outline of the 

 base of the tail (in the space between the anal and the caudal). The 

 two ridges are somewhat divergent in front of the luminous spots at the 

 base of the tail, but are almost touching between those spots. 



e. The first rudimentary caudal rays both above and below are 

 separated and form free spines. 



Finally, the edge of the neural ridge is finely crenulated, and the 

 height of the ridge is greater than that of the root of the tail. 



The colour, and the number of the photophores are in the main as 

 in A. olfersii: but the dark blue band extending (in both) along the dorsal 

 line, is divided in A. acideatus by a deep curve immediately beneath 

 the space between the neural ridge and the first dorsal; and the blue- 

 black colour, with extends obliquely out over the caudal, here reaches 

 beyond the middle of the lower rays of that fin. 



A. aculeatus was originally described (by Cu vier and Valen- 

 ciennes in 1849) from a specimen with a total length of about 65 mm. 

 taken in the sea off the Azores. 



