POLYGH^TA. 257 



one complete, 115 millims. long, tapering gradually behind; 8 millims. wide over 

 the seta?. 



This species has the same general appearance as the Psammolyce arenosa of the 

 Mediterranean. It is probably distinct in minor points, though I cannot specify what 

 these points are without comparing actual specimens. 



It differs from the preceding species in the following superficial respects : 



Ps. seylanica. 



1. Colour fuscous. 



2. Calcareous grains predominate. 



3. Venter beset with capillary papillse, i.e., 



Venter hairy. 



4. Terminal portion of dorsal cirrus of third 



segment slenderer and shorter than its 

 peduncle. 



Ps. riffida. 

 Colour fulvous. 

 Quartz grains predominate. 

 Venter beset with globular papillse, i.e., Venter 



tuberous. 

 Terminal portion of same cirrus tapering and 



longer than its peduncle. 



The parapodial armature of the two species shows such close correspondence that 

 the slight differences which are observable could easily be attributed to individual 

 variation, but the differences noted above under Nos. 3 and 4 would seem to preclude 

 the possibility of regarding them as co-specific. Unfortunately I have no information 

 as to the precise locality of the Psammolyce zeylanica. In Professor Herdman's 

 ' Narrative ' of his expedition, Psammolyce is recorded from two stations, LII. and 

 LIU. The latter is that from which the present species was dredged in 7|- to 

 9 fathoms, " bottom muddy sand with some dead shells ; " the former station may be 

 the locality of the other species, "between north of Cheval Paar and Vankali reef; 

 depth 3 to 6 fathoms ; bottom sand." 



The difference noted above in respect of the adventitious coating of sand-grains is 

 only of local significance as indicating a difference of habitat. The tuberculation of 

 the ventral surface of the body is the most obvious character of this species. The low 

 rounded dermal tubercles are placed close together without reference to segmental 

 limits and not in rows, forming an even, elastic sole on each side of the depressed 

 neural tract. The dermal tubercles are continued upon the parapodia, especially in 

 the posterior two-thirds of the body, where they are thickly covered. Besides these 

 spheroidal dermal tubercles there are tufts of filiform papillse like those shown on 

 Plate II., fig. 41. These occur on the base and summit of the parapodia, at the base 

 of the ventral cirrus, and there is a ventro-lateral tuft on each segment between the 

 tubercular tract and the parapodia. 



Other substantial differences between the two species are shown in the figures. 

 The elytra are formed upon the same model in both, and they are not safe objects for 

 comparison, since they vary from segment to segment. Those of Ps. rigida have a 

 concave anterior border, those of Ps. zeylanica are straight. The scar of insertion is 

 short in the former, elongated in the latter (Plate II., fig. 46). The setse of the 

 second segment have a shorter appendix (Plate II., fig. 47). An important difference 



2 L 



