70 CEYLON PEARL OYSTER REPORT. 



Clypeaster humilis, Laganum depressum, Antedon sp. (sev.), and Actinometra sp. ; 



Psammolyce sp. and other worms ; 



Polyzoa belonging to the genera Lepralia, Adeona, Crisia, and Scrupocettaria ; 



Melita obtusata, Erichthonius sp., Siphoncecetes sp. and other Amphipods, Elsia 

 indica and Lysianassa (? n. sp.), Lamhrus, Pleurophyllidia sp., and Kalinga ornata; 



Branchiostoma lanceolatum, and variety belcheri. 



The bottom Tow-net at 7 p.m. contained, amongst other Copepoda, Pontella 

 securifer, Ectinosoma atiantieum and E. roseum, Metacalanus aurivillii and Pseudo- 

 diaptomus aurivillii 22 species in all. 



At the end of the dav's work we anchored about 15 miles to the north of our 

 morning position on the Cheval with the view of spending the following two days in 

 working this northern end of the Gulf of Manaar, above the recognised paars. 



In the intervals of dredging and when moving from place to place, we were now 

 continuously engaged in examining the parasites of the pearl oysters and their 

 influence upon pearl formation. We also decalcified such small pearls as were found. 

 This work was continued as time permitted during the next few weeks, and also by 

 Mr. Hornell after I left. We found various parasites, in the liver especially, some of 

 which were Platyhelminthian and others Sporozoan in their nature, and some of which 

 were enclosed in calcareous capsides. Mr. Hornell afterwards determined that 

 these were Tetrarhynchus larvae of Cestodes, and we have no doubt that they are in 

 many cases the nucleus of the pearl, and the irritating cause of its formation. 



On March 7th, at 7 a.m., the sea-temperature was 79 - 5 F. and at G r.M. it was 

 80 F., about 10 miles south of Adam's Bridge. This day and the following one were 

 spent in continuous dredging in the northern end of the Gulf of Manaar, south of 

 Adam's Bridge, from south of Thanni-Kodi on Bameswaram Island to south of 

 Talamanaar on Manaar Island. Eight hauls were taken on the first day and 13 

 on the second, but although a wide extent of ground, about 18 miles from west to 

 east, was worked over no natural limits present themselves, and I consider it best 

 to unite the 21 hauls as a single locality (Station LIV.). We started at about 

 15 miles south of Thanni-Kodi and worked westwards into shallower water for two 

 hauls and then southwards into much deeper water (30 fathoms), the dredge eventually 

 falling "out of soundings." The 5th haul was in 40 fathoms at about 1G miles 

 south of Thanni-Kodi. Here we obtained Panthalis melanonotus, in a muddy 

 mucous tube very like the condition in which we find the same genus in water of the 

 same depth in the Irish Sea. We then ran north into 15 fathoms (6th haul) and 

 dredged eastward for the two remaining hauls in depths of 10 to 8^- fathoms, at 

 about 10 miles south of Adam's Bridge. We anchored for the night with Thanni- 

 Kodi bearing north, 18 W., and distant 10 miles. 



The following morning we began dredging at the same spot and worked eastwards 

 and then south-east through depths averaging 8 or 9 fathoms. In the 8th haul, 

 south of Talamanaar, we came upon a rough bottom of living coral at 4 to 5 fathoms. 



