i/3 



the lower margin with 8 or 9 spinules that increase in length, the longest of the three at the 

 apex being twice as long as the first or proximal spinule. Dactylus half as long as the carpus 

 and s / s of the propodus, 4-times as long as wide at the base ; the ventral hook, a little 

 shorter but almost 3-times as broad at lts base as the other, has a stout shape, being only 

 one and a half as long as broad at its base. These legs are nearly glabrous. Of the lifth 

 legs only the three first joints are present. 

 Length 1 1 mm. 



■&* 



Betaeus Dana. 



Only one species of Betaeus was collected by the "Siboga" and this species, Bet. indicus, 

 is new to science; it is very closely related to Bet. acquimanus Dana from New Zealand, but 

 it differs by the frontal margin being only very slightly emarginate and by the more slender 

 propodi of the three posterior legs. 



This genus comprises at present about 8 species the distribution of which is quite 

 peculiar and limited. Bet. aequimauits Dana, which differs from the other species by the deep 

 triang-ular emarg-ination of the front, inhabits the seas of New Zealand, Stewart Island and the 

 Warekauri or Chatham Islands. Bet. australis Stimps. occurs at Port Jackson and differs by 

 the frontal margin being convex and by the more slender legs. The third indopacific species 

 is the new Bet. indicus from the Sea of Lombok, where it lives at a depth of 1 8 m. At 

 no other localities of the whole Indopacific region a representative of this genus has hitherto 

 been observed. 



The other species inhabit the west coast of America. Bet. Harrimani Rathb., in which 

 the frontal margin is nearly straight, marked only with an almost imperceptible median sinus, 

 occurs at Sitka, and, according to Miss Rathbun, "represents a more northern latitude than 

 any Alpheid hitherto described". Bet. longidactylus Lock. inhabits the coast of California from 

 San Pedro to San Diego and Bet. Harfordi (Kingsley), which, according to Professor Coutière, 

 is identical with Bet. aequalis (Kingsley) = aequimanus Lock., ranges from Point Arena to 

 Catalina Island. Two species, finally, occur on the west coast of South America. Bet. scabro- 

 digitus Dana is found on the coast of Chili and has been observed at Valparaiso, Isla de 

 Pajaros, Bay of Arauco etc, after Coutière, however, this species should be identical with 

 Bet. emarginatus (H. M.-Edw.). The second, Bet. truncatus Dana, has been observed on the 

 shore's of Terra del Fuego (Hermite Island) and on the west coast of Patagonia. With this 

 species Bet. sinuosus (Guérin), recorded from Callao and the coast of Chili, should be identical 

 and this should also be the case with Bet. laevigatus (Nicolet) from Chili. 



f 1. Betaeus indicïis de Man. 



J. G. DE Man, in: Tijdschr. d. Ned. Dierk. Vereen. (2) Dl. XI, 1910, p. 309. 



Stat. 34. March 27. Anchorage off Labuan Pandan, Lombok. 18 m. Coral reef. 1 ova-bearing 

 female and 1 young specimen. 



Closely related to Bet. aequimanus Dana from New Zealand and representing this species 



41 



SIBOGA-EXPEDITIE XXXIXtf'. 23 



