322 "ENDEAVOUR" SCIENTIFIC RESULTS. 



pi. iv., fig. 12), who represents them as moderately long 

 and flagelliform ; this, however, is their appearance in 

 the variety coniger andamanensis, in which their tips fall 

 a little short of the middle of the ischial joints of the 

 thoracic legs. In both of these forms the vestigial arthro- 

 branch on the penultimate pair of legs is present as in all 

 the other "metapenei" except lamellatiis. The telson of 

 each of the specimens of coniger at hand has three pairs 

 of movable spines in advance of the fixed spines, as 

 described and figured by Alcock (op. tit., p. 25, pi. iv., 

 fig. 12). 



On the whole there seems to be a small ''Penceopsis 

 serratus" group within the genus in its broader sense, 

 the members of which have the inner antennular flagel- 

 lum of the male modified to form a more or less flattened 

 loop proximally and terminated by a knob or conical 

 denticle, which is situated at the base of the straight 

 portion of the flagelluin; the antennular flagella in both 

 sexes are as long as or longer than their respective 

 peduncles. The species of this group, P. serratus, Milne 

 Edwards (= mega-lops, Smith), rectacirius (Bate), 

 coniger and coniger var. andamanensis, Wood-Mason, 

 have usually short, more or less scale-like exopodites on 

 the thoracic legs (except in P. coniger var. andaina-nens'iN ) , 

 epipodites on all the legs except the last two pairs, and 

 no vestigial anterior arthrobranch on the penultimate 

 pair (except in P. coniger and coniger VSLT. andamanensis). 

 The telson is laterally armed with two or three pairs of 

 movable spines in addition to the distal, immovable pair. 

 If Milne Edwards and Bouvier are correct in stating that 

 Penceopsis serratus has an arthrobranch and one pleuro- 

 branch on the second maxillipeds instead of two arthro- 

 branchs, and if this character be present in the other 

 members of this small group, it might prove a more 

 valid feature to separate them from the rest of the 

 "Metapenei" than any other here set forth. 



SUBDIVISION OF THE GENUS PencBopsis. 



The species of Penwopsis are usually subdivided into 

 two groups on the basis of the absence or presence of 

 lateral marginal spines on the telson. 8 Of the first 



8 Alcock, Cat. Indian Decapod Crust. 1906, pt. iii., fasc. i., p. 49. 

 Id. De Man, "Siboga" Exped. xxxix.a, Decapoda, pt. i., Penseidae, 1911, 

 pp. 8, 54. Id. Pesta, Archiv f. Naturg. 1915, AM. A. Heft 1., p. 103. 



