PROCEEDINOS OF UNITED STATES NATIONAL MUSEUM. 67 



I>ESCRHI»TI©IV OF ATV APPARENTIiY NEW SPKCIE8 OF «-ASTEU- 



OSTEUS (G. ATfCINSai) FROM THE St!MOO»a€ ILAECES, MABNE. 



By TARI.ETOIV H. BEAM. 



In a large collection of fishes sent to the United States National Mu- 

 seum, in 1878, by Mr. C. Gr. Atkins, an assistant of the United States 

 Fish Commission, were six specimens of a stickleback which appears to 

 be undescribed, and for which I j^ropose the name given above, as a 

 slight recognition of Mr. Atkins's services as a collector and as an orig- 

 inal investigator into the rei)roductive habits of imiiortant fishes. 



Gasterosteus AtMnsii resembles in form and coloration G. pungitius 

 rather than the perhaps more closely related G. aculeatus. It may be at 

 once distinguished from all the other eastern American species by (1) 

 the presence of abont fitteen lateral plates, which rapidly diminish in 

 size after the fonrtli, and (2) its long ventral spines, which nearly or 

 quite reach the vent. The plates are quite unlike those of G. semiarma- 

 ti(S, being so thin and posteriorly so small that they are inconspicuous. 



For the purpose of description I have selected the individual whose 

 catalogue-number is 22492 a (collector's number, 3013). The extreme 

 length of this specimen is 35 millimetres, and its length to the origin of 

 the middle caudal rays is 30 millimetres, which is the basis of compari- 

 son for all the other measurements. 



The height of the body at the ventrals (.21) equals 3 times the length 

 of the npper jaw (.07), and 3 times the distance between the eyes (.07). 

 Its greatest width (.11) equals the long diameter of the orbit (.11). The 

 least height of the tail (.04) equals the length of the antecedent anal 

 spine (.04) and one-half the length of the snout (.08). The length of the 

 caudal peduncle (.13) somewhat exceeds the width of the head (.12). 



The length of the head (.31) equals 3 times the length of the mandi- 

 ble (.10). The length of the snout equals that of the operculum (.08). 

 The length of the upper jaw (.07) equals the distance between the eyes 

 and one-half the length of the post-pectoral plate (.14). The length of 

 the mandible (.10) is contained 10 times in the total length and equals 

 twice the length of the antecedent spine of the second dorsal (.05). The 

 long diameter of the orbit is contained 2f times in the length of the 

 head and 9 times in the total length. 



The teeth are as in the other members of the family. 



The spinous dorsal has two spines of equal length. Its distance from 

 the snout (.37) equals shghtly more than twice the length of the pecto- 

 ral (.18). The length of the two spines (.12) equals that of the first and 

 longest ray of the second dorsal (.12) and of the anal (.12). The spines 

 are in a straight line, and with each is connected a delicate membrane. 



The distance of the anal from the snout (.06) equals 6 times the long 

 diameter of the orbit. Its length of base (.18) equals 2J times the length 

 of the operculum. The length of the anecedent anal spine (.04) is con- 

 tained 3 times in that of the first and longest ray (.12). 



