's RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 61 



chela is 5 mm/ long and 1,36 mm. high, 3,7-times as long as high, 

 while the fingers are as long as the palm ; grooves on outer and inner 

 surface still hardly developed. Merus of 2nd legs 7,3-times as long 

 as broad, in the young male from Stat. 60, which is 13,5 mm. long, 

 the proportion between length and width of the merus is 7,5. Carpal 

 segments, in the male from Poeloe Weh, 1 mm., 0,92 mm., 0,33 mm., 

 0,32 mm. and 0,5 mm. long, the chela 0,94 mm., fingers as long as 

 palm; the 1 st segment is 5-times as long as thick at its distal extremity, 

 the 2 nd 4,6-times as long as wide in the middle. In the young male 

 from Stat. 60 the 1 st segment appears to be 4,54-times as long as thick 

 at distal extremity, the 2 nd just 4-times as long as thick in the middle. 

 Merus of 3 rd legs in the male from Poeloe Weh 4-times, in that from 

 Stat. 60 4,55-times as long as wide in the middle, presenting in the 

 last mentioned specimen already nearly the same proportion as in adult 

 individuals ; propodus of 3 rd legs in the male from Poeloe Weh 5,7-times 

 as long as broad in the middle, in the male from Stat. 60 6-times. 



Alpheus crassimanus, which is distributed throughout the Indian Ar- 

 chipelago and also known from Djibouti, at the southern extremity of 

 the Red Sea, was discovered in 1865 by the Novara Expedition at the 

 Mcobar Islands, in the immediate neighbourhood of Poeloe Weh. 



EXPLANATION OF PLATE I. 



Fig. 1. Callianassa (Callichirus) vigilax n. sp. Carapace and both pairs of an- 

 tennae, X 2. 



Fig. 2. Anterior part of carapace with the eye-stalks and the two pairs of an- 

 tennae, X 6. 



Fig. 3. Caudal fan, 6 th somite and posterior end of 5 th , X 2. 



Fig. 4. Right maxilliped of 3 rd pair, X 4. 



Fig. 5. Left leg of 1st pa i r) x 4. 



Fig. 6. Distal part of carpus, propodus and dactylus of right leg of 3 rd pair, X 4. 



