RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 57 



VI. — DESCRIPTION OF A NEW SPECIES OF THE GENUS CAL- 

 LIANASSA LEACH AND OF A SPECIES OF THE GENUS ALPHEUS 

 FABR., BOTH FROM THE INDIAN ARCHIPELAGO. 



BY Dr. J. G. DE MAN. - (WITH PLATE I). 



Callianassa (Callichirus) vigilax n. sp. 

 Plate I, fig. 1—6. 



One female without eggs, collected in 1863 by Mr. Ludeking at 

 Amboina. 



This new species .is most closely related to Callianassa {Callichirus) 

 armata A. M. - Edw. from the Fiji Islands, but may at first sight be 

 distinguished by the shape of the abdomen, of the caudal fan and of 

 the smaller cheliped, probably also by that of the larger, which, unfor- 

 tunately, is wanting, like the flagella of the outer antennae. 



This specimen is 85 mm. long from tip of rostrum to end of telson 

 and therefore belongs to the larger species of this genus; the carapace 

 which is 22 mm. long, measures about one-fourth the whole length and 

 one-third the length of the abdomen. Rostrum (Fig. 2) broadly trian- 

 gular, acuminate, reaching to just beyond the middle of 1 st antennular 

 article and to the distal third part of the ophthalmopods, just beyond 

 the eyes-; upper surface of rostrum slightly convex transversely and 

 longitudinally, obliquely directed downward in a lateral view, while the 

 acute rostral point is directed horizontally forward. Like in Call, armata 

 (A. Milne Edwards, Nouv. Archives du Muséum. Mém. 1870, T. YI, PLI, 

 fig. 1), the anterior margin of the carapace is armed, on either side of 

 the rostrum, with a smaller acute spinule, just outside the eye-stalks; 

 these spinules are directed obliquely inward and almost half as long as 

 the rostrum, reaching as far as the distal margin of 1 st antennal article. 

 The gastric region (Fig. 1) which is twice as long as broad and strongly 

 convex transversely, is separated anteriorly by a slight depression from 

 the rostrum; cervical groove and lateral grooves, defining the gastric 

 region, exactly as in Call, armata. Lineae thalassinicae straight, slightly 

 converging in their anterior half, their posterior half running parallel. 



Like in Call, armata the 6 th somite of the abdomen (fig. 3) is the 

 longest of all and presents precisely the same shape and characters as 

 in this species. Next of length is the 2" d somite, which is but little, 

 viz. one ninth, shorter than the 6 th ; while according to the figure, in Call. 



29—111-1916 



