178 CEYLON PEARL OYSTER REPORT. 



Callochiton platessa (Gould) ? 



A single specimen, not in very good condition, from the lagoon inside the coral reef 

 at Galle. 



Ischnochiton ravanae, n. sp. Plate I., tig. 4. 



Shell elongate, well elevated. Ground colour white, blotched and marbled with 

 varying colours, black and purple predominating. Sculpture on the lateral areas, 

 well-marked riblets, generally with an angle in the centre of the ribs, pointing 

 towards the girdle ; median areas smooth to the eye, but microscopically punctate. 

 Sculpture of the posterior portion of the posterior valve similar to the lateral areas. 

 The anterior valve is marked by slight depressed distant riblets, similar to lines of 

 growth. Interior white, slightly tinted with yellow. Anterior valve with 8, median 

 1, posterior 15 slits. 



Girdle scales broad, flat, thick, strongly striated. 



Length, when alive, about 25 millims. 



Hab. : Donnan's Muttuvaratu Paar, 8 fathoms (one specimen). 



Ischnochiton herdmani, n. sp. Plate I., fig. 6. 



Shell much elongated, narrow, moderately elevated. Ground colour a greenish- 

 grey with delicate marking of brown, green, yellow, &c. 



The sculpture is difficult to describe ; the anterior valve and posterior area of the 

 posterior valve are marked by a number of concentric ridges, the edges of these ridges 

 being broken and roughened ; the lateral areas of the median valves are similarly 

 sculptured ; the anterior portion of the posterior valve and the median areas are 

 marked by a number of crossing lines, which give the appearance of the shell having 

 been stabbed with a broad, blunt dagger ; on the jugal tract these lines lengthen out 

 and the stab-marks become finer and much more elongate. Interior white, tinged 

 with pink. Anterior and posterior valves with 9, median with 1 slit. 



Girdle wide, with squarish flat, well striated, scales. 



Length, when alive, about 40 millims. 



Hab. : The lagoon inside the coral reef at Galle (three specimens). 



Related to /. alatus, Sby, but more depressed and differing in sculpture. 



Ischnochiton ferreus, n. sp. Plate I., fig. 5. 



Shell ovate, eroded and covered with a brown rusty staining, but apparently 

 whitish below. Sculptured on the median valves with about ten radiating riblets on 

 the lateral areas and distant longitudinal riblets on the median areas. The anterior 

 valve and posterior valve (behind the mucro) appear to be sculptured as the lateral 

 areas. 



