220 CEYLON PEARL OYSTEE REPORT. 



female was 35, 12, 8 total, 55. There is, therefore, quite a close agreement between 

 the two. 



The best distinguishing feature of this species is the dorsal tin, which is so markedly 

 swollen at its anterior end. This feature alone is usually quite a sufficient indication 

 of the species (fig. 8). In A. cingalense the dorsal fin is slightly swollen at its 

 anterior end. This condition is somewhat more emphasised in A. maldivense, a new 

 species lately described by Forster-Coopee, from the Maldives (8). This new species 

 seems to bear a remarkable resemblance to the specimens of A. cultellum, from 

 Ceylon. The resemblance in the shape of the fins in particular is striking. In both 

 the Ceylon specimens of A. cultellum the fin rays are absent from the ventral fin 

 chambers. 



The female specimen is well preserved and shows the notochord to be distinctly 

 knobbed, one of the chief characters of the species (fig. 8). The male specimen is not 

 so well preserved and does not show this knobbed notochord. In both specimens the 

 dorsal fin overlaps the nervous system, and the notochord is prolonged in front of the 

 dorsal fin rather more than Kirkaldy shows (figs. 8 and 9). The caudal fin also 

 differs somewhat from Kirkaldy's figures, for while in the latter it is deeper and 

 well marked off from the rest of the fins, in the Ceylon specimens the dorsal and 

 ventral fins fade insensibly into the caudal fin, as shown in A. maldivense (8). 



I have been able to confirm Kirkaldy in finding sensory-papillae on the oral cirri 

 of this species. Willey (4) had previously stated that the cirri were smooth. The 

 papillae were distinctly present in the female specimen from Ceylon. 



CONCLUSIONS. 



The whole collection has proved of very great interest in many ways. Although 

 no new species are recorded, the fact that seven species (including var. belcheri) 

 of the group occur round I leylon, indicates the great wealth of the Acraniate fauna of 

 these waters. 



Four species are recorded from this neighbourhood for the first time BranGhiostoma 

 pelagicum, B. calij hmiense, />'. indicum, and Asymmetron cultellum ; while our 

 knowledge of the geographical distribution of nearly all the species has been extended 

 bv this collection. 



As regards the habitat of the animals, we have some indication in this collection 

 that they live commonly in a clean coarse sand, made up, at least to some extent, of 

 the shells of the large Foraminifera Orbitolites and Heterostegina. 



The depths at which the specimens were taken range from 3 to 14 fathoms, in all 

 cases comparatively shallow water. 



