GASTKOSTEUS. 107 



1. GASTROSTEUS, 

 Linn. Syst. Nat. i. p. 489 (176G), part. ; Ciiv. it Val. Hist. Poiss. iv. p. 479 (1829) ; 

 Giinth. Cat. Y\<h. i. p. 2 (1859), part. 

 Body moderately elongate. Snout short, not tubiform. Villiform 

 teeth in jaws, none on palate. Dorsal fin with 3 to 11 spines, soft part 

 similar to anal. Pelvic bones united to form a triangular or lanceolate 

 plate between the ventral fins. Vertebnc 29-33. 

 A single species in Africa. 



1. GASTROSTEUS ACULEATUS. 

 Linn. S. N. i. p. 489 (17(;C.). 



This species, widely distributed in the seas and fr(;sh waters of the 

 cold and temperate ]iarts of the Northern Hemisphere, is represented 

 in the fresh waters of Algeria by the following form, which may be 

 designated as var. alf/eriensis : — 



Gasterostevs hwms (non C. & V.), Gerv. Zool. Pal. Gen. p. 202, pi. xlv. fi<;. 1 (1809). 

 Gaxterosteiis hravhycentrus (non 0. ct V.), Playf. k I.otoum. Ann. & Jlao-. N. H. (4) 



viii. 1871, p. 388. 

 GaMerostevs ahjeriensis, Sauv. N. Arch. Mus. x. 1874, p. 17 ; Regan, Ann. & Mag. 

 N. II. (8) iv. 1909, p. 4:57. 



Fig. G.;. 



Gastrosteiis aculeattis, var. ahjeriensis. x Ij. 



Depth of body H to i times in total length, length of head 3^ 

 to 3i times. Snout as long as or a little shorter than eye, which is 

 3 to 3^ times in length of head. D. I, I, 111-12 (rarely 1, I, I, I 12) ; 

 spines rather narrow and feebly denticulated at tlie sides, first and 

 second equal or second the longer, usually measuring less than diameter 

 of eye, first behind vertical of base of pectoral. Anal I 8-9. Ventral 

 spine i to I length of pelvic plate. 1-4 bony plates above the 

 ascending process of the pelvis, body sometimes entirely naked; no 

 lateral keel on the caudal peduncle. 

 Total length 50 millim. 

 Metidja, near Algiers. 

 1-3G. Ad., ligr., & vg. Ditches in the Metidja. Sir L. Play fair (P.). 



