154 On a new C yprinodont Fish. 



Length 6 mm. 



Very near G. nana, G. 0. Sars, from wliicli it diflfers in 

 the smaller antennular appendage and the form o£ the first 

 joint of the last two pairs of perajopods, and especially in the 

 much greater length of the lower antennae. 



Seba antarcdca, sp. n. 



W.Q. Oct. to jMarchj 1902 : in sponges. Two large males, 

 19/3/02 ; 10 fatli. 



The females and young males (which differ from the 

 females only by the absence of the incubatory lamellfe) 

 cannot be distinguished from S. Saundersi, Stebbing, with 

 which this species may be identical*. The two large males 

 mentioned above, however, show such a marked difference in 

 the great development of the meral joints of the last three 

 })airs of peraeopods, that at first sight I look them for a 

 distinct species. As, however, they were associated with the 

 smaller form, with which they agree in the rest of their 

 structure, I have no doubt that they are only full-grown 

 males. It may be remembered that in the adult male of our 

 own Orchestia littorea (Mont.) we have a similar enlargement 

 of the meral joint in the last pair of per^eopods. 



XXIV. — Description of a new Cyprinodoat Fisli of the Genus 

 J enynsia from Aryentina. By C. Tate Regan, B.A. 



Jenynsia maculata. 



Depth of body 3| to 4 in the length, length of head 3? 

 to 4. Snout as long as or shorter than eye, the diameter of 

 ■which is 3| to 4 in the length of head, interorbital width 2 

 to 2^. Body regularly and completely scaled ; 28 to 30 

 scales in a longitudinal seiies. Dors^al 8-9 ; origin equi- 

 distant from extremity of operculum and base of caudal or 

 fi'om eye atul end of caudal. Anal 8-9, opposite to the 

 dorsal (?) or a little in advance of it [S)- Caudal rounded 

 or subtruncate. Pectoral about | the length of head ; 

 ventrals extending to the vent. Sides with 3 or 4 irregular 

 scries of more or less oblong blackish spots. 



Several examples, measuring up to 73 mm. in total length, 

 from Cachi, Salta, Argentina, at an elevation of 2.")00 metres, 

 collected by II err J. Steinbach. 



This species is very close to Jenynsia lineata, Jenyns, 

 which has the dorsal fin a little more advanced and has the 

 spots on the sides smaller and more nunu-rous, forming 

 regular longitudinal lines along the series of scales. 



* Ann. & .M;ig. Nat. Hist. ser. 7, vol. xvii. (1900) p. r,G9. 



