]82 CEYLON PEARL OYSTER REPORT 



Family : PHOXICHILIDJv 



Phoxichilus, Latr. 



Phoxichilus mollis, n. sp. Plate, figs. 1-7. 

 Length 5 millims. Body proportioned as in P. Icevis, Grube,* but almost entirely 

 unarmed, only a few minute spines on the lateral processes and on the head-segment 

 (figs. 1,2). Femur of each leg evenly swollen distally without angular projections, 

 armed only with a series of minute spines along the edges and four terminal spines 

 (figs. 1, 3). Male with 24 cement glands on each femur (figs. 3, 4, e.g.). False leg 

 of male with 6th segment greatly thickened and enlarged laterally (figs. 5, 6). 

 Propodus with 5 stout basal teeth (the 3rd the longest) and 6 small distal teeth 



Habitat : Coasts of Ceylon. Two males and several females picked off experimental 

 oyster cage hung over side of ship on the North-East Cheval Paar, loth February, 

 1903. Cheval Paar, 2 males, one with eggs and one young female. Deep water off 

 Galle ; young female. 



The above characters will serve to distinguish this species from any form of 

 Phoxichilus hitherto described, the feeble armature of the trunk and femora being 

 the most striking character. The armature of the tibial segments, though feebler 

 than in the European forms, approaches the usual type of the genus, while the tarsus, 

 propodus, and claws differ but slightly from those of other species of Phoxichilus. It 

 seems, therefore, that the loss of spines begins on the trunk and extends slowly 

 towards the extremities. 



The two forms of Phoxichilus most nearly related to the present species are 

 P. meridionalis, Bc>HM,t from Singapore, and the problematical P. inermis, Hesse.j 

 The former of these, however, has very prominent spines on the femur, and seems to 

 approach P. Icevis rather closely, while the latter is said to be 10 millims. long, with 

 almost entirely unarmed legs and a 3-segmented abdomen (the last statement needs 

 confirmation). 



I have elsewhere drawn attention to the slight comparative characters by which 

 the various described forms of Phoxichilus are distinguished from one another, and I 

 think it likely that when specimens of this genus have been obtained from many 

 other parts of the world, it will be impossible to maintain " sjDecific " distinctions. 

 Already we have a series beginning with the well-armed P. spinosus, Mont., passing 

 through P. Icevis, Grube, P. vulgaris, Dohrn, P. meridionalis, Bohm, to P. mollis 

 and P. inermis, Hesse, in which the spiny armature has become, to a great extent, 

 lost. And it is of special interest in this connection to note that in one of the Ceylon 



* 'Abhandl. d. Schlos. Gesellseh. f. vaterl. Guitar,' 1869-72, p. 124-126, Taf. 1, fig. 1. 

 t 'Monatsber. d. Konigl. Akad. Wissensch. Berlin,' 1879, p. 189-191, Plate 2, fig. 4. 

 t 'Ann. Sci. Nat.' (Zool.), (5), vii., 1867, pp. 199-201. 

 'Sci. Proc. R. Dublin Soc.,' vol. viii., 189.., pp. 200-202. 



