334 CEYLON PEARL OYSTER REPORT. 



pair of denticulations being very large. The 1st lateral tooth is strong, with a broad 

 somewhat rectangular base and an irregularly serrulate or smooth outer margin. In 

 the 2nd tooth the margins are smooth and the point entire. The 3rd tooth has a 

 small sub-apical denticle on the outer margin. This denticle is found on all the teeth 

 outwards till the outermost one is reached ; it increases in size outwards, so that the 

 lateral teeth are for the most pai*t bifid or, in a few cases, trifid. The outermost 

 tooth is simple. This specimen differs slightly as to its radula from that examined 

 by Bergh, in which the apical denticulation begins on the 5th tooth and is absent 

 from the 3-6 outermost. It agrees, however, in other respects. The other Ceylon 

 species, P. ceylanica, has, like P. formosa, the lateral teeth bidentate, but differs in 

 having a much smaller number of lateral teeth and in having the outermost teeth 

 finely serrulate. 



Lingiiella cinerea, n. sp. Plate I., figs. 10 to 13. 



A single specimen of this species was dredged 10 miles north of Cheval Paar. 



Length about 1'5 centims., width 1*4 centims., width of foot 0*9 centim. 



Mantle moderately smooth, of a greenish-grey colour, which is denser on the head 

 and front of cloak. The margin of the cloak studded with distant tubercles marked 

 with a ring of grey, becoming larger towards the centre of the back and merging into 

 irregular raised areas separated by deeply pigmented grey furrows. 



Lateral margin of underside of mantle with a band of opaque yellow cnidopores, 

 2 to 3 deep. Lateral lamella? about 32, slightly oblique. 



Radula of 35 rows, formula 46-1-46. The central tooth (Plate I., fig. 10) has a 

 median spine with 3 lateral serrulations, and 3 lateral denticulations. The 1st 

 lateral tooth with about 9 denticulations on the outer edge. The teeth increase in 

 length outwards, the number of denticulations decreasing (Plate I., fig. 12), and the 

 two outermost teeth being smooth (Plate I., fig. 13). 



The jaw plates (Plate I., fig. 11) of the usual form, strongly curved (in the figure 

 they are flattened out), of a dark horn colour. 



This species seems outwardly to come rather near to L. sarasinica, Bgh., from 

 Ceylon, but differs in not having the tubercles densely crowded on the mantle edge. 

 The radula also is very different both in form and number of teeth. 



NUDIBRANCHIATA HOLOHEPATICA. 



DO RIDIAD^ CRYPTOBRANCHIAT.E.) 



Sub-family : HEXABRANCHID^E. 



Hexabranchus marginatus, Q. and G. 



There are in the collection two specimens of Hexabranchus, both from Periya Paar, 

 which I think it is probable belong to this species. One specimen is very small, 



