﻿ALPHEUS BICOSTATUS. 



103 



obliquely backward, about to the level of the small, median 

 tubercle. Orbits prominent, as in A. bidens, grooves between 

 the orbits and the rostral carina broad, moderately deep. 

 Frontal margin at either side, close to the orbits, with a 

 slender spine as in A. cristatiis, these spines about one 

 third the length of the rostrum proper. 



Carapace with an acute, well-developed, though small, 

 pterygostomian spine. 



Antennal and antennular peduncles and thoracic legs 

 similar to those of A. bidensy but the dactylus of the 

 smaller chelipede of the male, which also presents the 

 Balaeniceps-shai^e, appears broader in proportion to its 

 length and more flattened, whereas the palm presents no 

 trace of a transverse groove. 



Length of male 18,5 mm., of female 20,5 mm. 



6. Alpheus praedator, n. sp. 



Station 181 or 231. Ambon. Reef-exploration. 



Another new species of the group „ins{gnis" Cout., 

 closely related to A. bidens (Oliv.). 



Rostrum acute, narrow, reacting to the middle of 2"^ 

 joint of antennular peduncle. Rostral carina interrupted, with 

 a small, obtuse tubercle just behind the interruption, as in 

 A, bidens ] interorbital part of rostral carina strongly com- 

 pressed, sharp-edged and rising, between the corneae and 

 the interruption, to a high, arcuate crest. The obtuse 

 tubercle is continued in a straight, obtuse crest, that 

 reaches to the posterior third of the carapace, bounded at 

 either side by a shallow groove or depression, that ends 

 abruptly at the posterior extremity of the crest. At either 

 side of the rostral carina, at the base of the eye-hoods, 

 a pointed tooth, broad at its base, as in A. bidens ] orbits and 

 frontal margin also as in this species. 



Second joint of antennular peduncle one and a half 

 as long as thick, little longer than the two other joints that 

 are of equal length ; 1st joint with 2 spines as in A, bidens. 



Notes from tlie Leydeii IMuseum, Vol. XXX. 



