CLASS PISCES. 149 



Two species are confounded together under the 

 name of Gasterosteiis aculeatus, Lin., which have three 

 free spines on the back. One of these species, G. 

 trachuriis, Cuv., Bl., pi. liii. f. 3. has all the sides to 

 the end of the tail covered with scale plates. The 

 other G. gymnurus, Cuv. Willughb. 341, has these 

 plates on the pectoral region only. One or other of 

 these appears sometimes in such prodigious numbers 

 in certain waters in England, and in the north, that 

 they are made use of to manure the land, feed pigs, 

 make oil, &c. ! 



G. pungitius, Lin., BL, 53, 54. 



Is the smallest fish of our fresh water. It has nine 

 very short spines on the back ; the sides of the tail 

 have some carinated scales ; but there is also in our 

 fresh waters a species nearly allied to this, G. loevis, 

 Cuv., which is without this armour. 



We might make a separate subgenus of 



Gast. spinochia, Lin., BL, 53. 1. 



The sea Gasterosteus, thin and elongated in form, 

 with fifteen short spines on the back, and all the 

 lateral line covered with carinated scales. The ven- 



1 Approximating species, or Gasterostei, with three spines, are G. 

 argyropomus, Cuv. ; G. brachycentrus, Cuv. ; G. tetracanthus, Cuv., 

 three species from Italy ; G. noveboracensis, Cuv. ; G. niger, Cuv., 

 or biculeatus, Mitchill, New York Trans, i. 1. 10; G. quadracus, 

 id. ib. f. 11 ; G. cataphractus, Tiles. Mem. de l'Acad. de Petersb. 

 Hi. 8. 1. 



