324 CEYLON PEARL OYSTER REPORT. 



This specimen resembles Pteroeides lacazei, var. npinosum, in having one row of 

 zooids, in the termination of the axis, in the number and composition of the main rays 

 and in the texture of the pinnules. 



Locality : Station XXI., Back Bay, Trincomalee, 8 to 12 fathoms; Station LXIIL, 

 West of Periya Paar, 40 fathoms. 



FAMILY: VEPtETILLID^l. 



Cavernularia obesa, VALENCIENNES. 



This species is represented by a number of specimens obtained from shallow water 

 in the northern part of the Gulf of Manaar. The largest specimen is evidently only 

 the upper portion of a large colony. The part measures 61 millims. in height, and 

 has a diameter which varies from 10 millims. near the tip to 17 millims. near the 

 lower end. In shape it is irregularly elliptical. 



The autozooids are scattered over the surface, and the parts not occupied by the 

 autozooids are thickly beset with siphonozooids. The position of the autozooids, 

 which are all retracted, is marked by bluish- to brownish-black spots. 



A cross-section in the lower part shows four large central canals which run parallel 

 to the long axis of the specimen and are apparently continuous. Radiating from the 

 central part thus formed numerous canals can be seen, some of which run down to 

 the central canals, others end blindly, and others join with one another. Some of 

 the larger canals seem to open into one or other of the four central canals. 



The spicules are perfectly smooth rods, with blunt ends, some cut abruptly across, 

 others slightly tapered and rounded. 



Another specimen, which is quite complete, probably belongs to the same species. 

 It has a total length of 53 millims. and a rachidial diameter of 7 millims. near the 

 tip. The rachis is slightly elliptical in cross-section, but becomes almost cylindrical 

 near the tip. The whole surface not occupied by the autozooids is covered by 

 numerous minute wart-like bodies which represent the upper parts of the siphono- 

 zooids. 



The autozooids occur scattered over the whole surface, and all are almost com- 

 pletely withdrawn. The incurved tentacles are just visible on the surface as 

 brownish- to bluish-black circles. There is a marked difference between the 

 autozooids in size, but this is probably due to a difference in the state of retraction. 



The stalk is marked off from the rachis by an abrupt diminution in size, and it, 

 with the lower part of the rachis, is marked by a number of grooves which run 

 parallel to the length of the specimen. 



Localities: Station LIT., near Vankali Reef, Gulf of Manaar, 3 to 6 fathoms; 

 and Cheval Paar. 



