180 CEYLON PEAEL OYSTER REPORT. 



minute, crossing riblets, somewhat as is frequently seen in the Pectinidte. Anterior 

 valve, posterior portion of posterior valve, and lateral areas marked with flattened 

 nodules, those on the median valves being fewer in number, irregular in size, and 

 more Avidely separated. Mucro posterior and much elevated. 



Interior white. Median valves with 1, anterior with 8, posterior valve with 

 numerous small slits. 



Girdle microscopically setose. 



Length, when alive, about 18 millims. 



Hab. : Pearl-banks in the Gulf of Manaar and deep water off Galle (Stn. XL.), 

 34 fathoms (two specimens). 



EXPLANATION OF PLATE I. 



Fig. 1. Tonicia pectinoides, n. sp. 



Fig. 2. Acanthochites penicillatus (Desh). 



Fig. 3. Calldchitoti siibkevis, n. sp. 



Fig. 4. ' Ischnochiton rammce, n. sp. 



Fig. 5. Ischnochiton ferreus, n. sp. 



Fig. 6. Ischnochiton herdmani, n. sp. 



Fig. 7. Craspedochiton lagueatus (Sby). 



