314 CEYLON PEARL OYSTER REPORT. 



described in 1899.* The present little specimen from Ceylon (fig. 25) agrees 

 perfectly in external characters, including the spines and the remarkable stellate 

 hairs (figs. 26 to 29), forming a fine down over the surface of the test, with the 

 Australian specimens. 



Cynthia aripuensis, n. sp. Plate III., figs. 30 to 39. 



External Appearance. Body of irregularly globular or pyriform shape, with the 

 narrower anterior end cleft into the two long crumpled siphons. The branchial siphon 

 is especially long (fig. 31). Attached by the posterior end. Surface corrugated. 

 Colour, creamy yellow, browner in places ; some specimens have a pink tinge. Size of 

 a large specimen, 4 centims. x 2'5 centims. x 1'5 centims. 



Test leathery and tough, up to 2 millims. in thickness, wrinkled on the outer 

 surface, creamy yellow, smooth and glistening on the inside, white in section. The 

 invaginated test lining the siphons bears slender sharp-pointed scales (fig. 33). 



Mantle strong, opaque anteriorly, more membranous and transparent posteriorly, of 

 a yellowish colour becoming red on the siphons. Strong muscle bundles radiate from 

 the bases of the siphons (fig. 35). 



Branchial Sac with six folds on each side. About nine to twelve internal bars on 

 the fold, and four to six rows of meshes in the interspace. There are three smaller 

 transverse vessels between each pair of much larger ones (fig. 32). The mesh is 

 transversely elongated, contains about six rather small stigmata, and is divided by a 

 horizontal membrane. Parasitic Copepoda are present in the branchial sac. 



Dorsal Lamina, represented by closely placed long tentacular languets (fig. 37). 



Tentacles large, much branched, and closely placed; about 18 larger ones and the 

 same number of very much smaller ones placed so that the bases touch (fig. 36). 



Dorsal Tubercle simple, ovate in outline, with the opening anterior or lateral, and 

 the horns coiled slightly inwards (figs. 38, 39). 



Gonads large, yellow ; present on both sides, in a double row of about 20 masses. 



Locality : (1) Aripu coral reef, shallow water, about a dozen specimens ; (2) " Gulf 

 of Manaar," four specimens; (3) Station LXVL, off Mutwal Island, 10 to 35 fathoms, 

 three specimens ; (4) Station IV., off Karkopani, 6 to 9 fathoms, two specimens. 



This is probably a fairly common Cynthia, in the Gulf of Manaar, as a number of 

 specimens were obtained while wading on Aripu coral reef, of which about a dozen 

 were preserved. The specimens dredged off Mutwal Island are certainly the same 

 species, although the shape is a little longer and less globular (fig. 30). That slight 

 difference may well be due to the place of attachment or to the accidents of 

 preservation. The internal organisation is the same as in the Aripu specimens. 



This species recalls Sluiter's Halocynthia polycarpa from the "Siboga" expedition, 

 but differs notably in the tentacles and the dorsal tubercle, and in the details of the 

 branchial sac. From Roule's //. corallina this species also differs in several 



* ' Descriptive Catalogue (No. XVII.) of Tunicata in Australian Museum,' Sydney, 1899, p. 34. 



