GENERA AND SPECIES. IOI 



much wider than the upper. The teeth are large and sharp, and 

 have the inner edge serrated. The colour is grey above without 

 spots, and whitish below. The largest British specimen measured 

 7 feet. 



Casterosteus. Plate xii. GASTEROSTEIDM. 



Spines more than three 



97. spinachia, FIFTEEN-SPINED STICKLEBACK. Spines 15 or more; 

 snout produced, body long. 



96. pungitius, NINE-SPINED STICKLEBACK. Spines 8 ton 

 95. spinulosus, FOUR-SPINED STICKLEBACK. Spines 4. 



Spines three 



94. gymnurus, SMOOTH-TAILED STICKLEBACK. Plates extending to 

 tip of pectoral. 



93. scwiarmatus, HALF-ARMED STICKLEBACK. Plates extending half- 

 way to base of caudal. 



92. trachitms, ROUGH-TAILED STICKLEBACK. Plates keeled at base of 

 caudal. 



91. acidcatus, THREE-SPINED STICKLEBACK. Spines very short. 



The Fifteen-spined Stickleback is a sea fish, and in other ways 

 differs greatly from the others. The fore part of its dorsal fin is repre- 

 sented by 15 or 17 isolated spines, the hinder part consisting of 6 or 

 7 rays ; in the anal there are also 6 or 7 rays ; in the caudal there 

 are 12 or 14 ; in the pectorals 9 or 10 ; and the ventrals have only 

 one spine and one ray. The second dorsal is over the anal, and 

 begins in the middle of the back, the hinder portion of the fish being 

 long and slender. Along the body is a row of ridged plates, with 

 shorter ridges above and below it, all three ending at the base of 

 the tail. The snout is long, and the eye is placed halfway between 

 its tip and the first spine. In colour this species is olive, with 

 silvery underparts, and it has a silver stripe along the snout ; but 

 under excitement the colour is changeable. In length it measures 

 7 inches. It is found in rocky pools and among seaweed-covered 

 rocks, where it makes a nest under one of the overhanging fronds, 

 lacing together and affixing to it a sort of open ball of the softest 

 and silkiest weeds around. This nest is watched over by the male 

 until the young are about a month old. 



The Nine-spined, otherwise the Ten-spined, Stickleback is a 

 fresh-water species. The isolated spines representing the fore-half 

 of the first dorsal number from 8 to n, the rays number 9 or 10, 

 and have a short spine to begin with. In the anal there is a short 

 spine and 8 or 10 rays ; in the caudal there are 12 rays ; in the 

 pectorals 10 ; and the ventrals are represented by a spine and a 

 ray, or are absent altogether. In colour this species is olive green 

 or brown above, the sides silvery spotted and dotted with black, and 

 the fins transparent. In the breeding season the underparts become 

 blue or red. The length is from 2 to 3 inches. The nest built by 

 this species is like a muff in shape, and consists of soft-leaved 

 water plants, the finest being confervoid filaments. 



