746 ME. AV. F. LANCHESTER ON CRUSTACEANS [Jun© 19, 



I note the following sexual differences in this species: — 



Males. The hind margin of the abdomen as seen from below 

 (t. e. bind margin of 3rd segment) is medianly emarginate, and 

 curved forward at tbe sides. The first and second sternal seg- 

 ments are crossed by transverse rows of granules, whicb are 

 prominent in the larger examples. 



Females. The hind margin of the abdomen not, or very faintly, 

 emarginate, and almost transverse ; first and second sternal seg- 

 ments smooth. 



Dim. o* 15-5 x 9-5. d 15x9. 6 15-5x9. <3 10-5x6. 

 6 12x19. 2 4-75x8. 



XXXVIII. Genus Achelous de Haan. 



62. Achelous whttei A. M.-Edw. 



Achelous ivhitei, A. M.-Edw. Arch. Mus. t. x. p. 343, pi. xxxi. 

 f. 6 (1861); Walker, Journ. Linn. Soc, Zool. vol. xx. p. 110 

 (1887) ; Henderson, Trans. Linn. Soc, Zool. vol. v. p. 371 (1893). 



Hah. Singapore ; up to 12 fms. An adult male and adult female ; 

 a spurious male, with the whole of the under surface covered with 

 parasitic organisms, and a spurious female, less densely beset with 

 the same parasite ( = a SaccuVna). In the adult female the last 

 (epibranchial) spine is but little bigger than those in front, and the 

 breadth of tbe carapace is relatively less than in the male. 



Dim. <3 18x11-5. $ 16x12. 



f 63. Achelous rubro-marginatus, sp. nov. (Plate XLVI. fig. 8.) 



Hah. Singapore ; taken from off a floating piece of wood. A 

 single specimen, a female. 



Carapace only moderately broad, and somewhat convex, covered 

 with numerous, evenly disposed, and granulated prominences, 

 between which is an exceedingly dense, short pubescence ; this 

 extends on to the prominences, but not so as to conceal the 

 granules on them, which are quite smooth and rounded. Frontal 

 lobes six : two median, short and conical, separated by a wide 

 fissure from the submedian, which are broader and directed more 

 obliquely outwards than the median, but do not project farther 

 forwards ; a deeper, wider, fissure separates these from the laterals, 

 which are broad and less prominent, and form the internal or- 

 bital angle. All these lobes are granulated. Superior orbital 

 margin granulated, with two fissures ; tooth of external angle broad 

 and salient ; tooth next behind this about half the size, and the six 

 anterolateral teeth following equal, and still smaller than the 

 second, all directed forwards ; last tooth strong, a very little larger 

 than the external tooth of the orbit, and with its point curved 

 forwards. Lower orbital border granulous, with a deep fissure 

 in its external half ; internal angle of this lower border forming 

 a strong and prominent tooth. Basal joint of antennae broad, 

 and reaching the infero-lateral process of the front, next joint 

 moderately dilated ; flagellum smooth and not very long. Ischium 



