216 CEYLON PEARL OYSTER REPORT. 



The posterior extension of the notochord past the myotomes is not very great. 

 The ventral fin has fin chambers which are also extended postanally, as in 

 B. lanceolatum and Asymmetron hectori. In the latter species the chambers extend 

 postanally to the antepenultimate myotome, while here they extend only five 

 myotomes posterior to the anus. The ventral fin rays are double, and are not 

 extended postanally as in A. hectori. Willey did not notice the postanal extension 

 of the fin chambers in his specimens. Only the larger specimen here has ventral fin 

 rays, showing again what was noticed under B. lanceolatum, var. belcheri, that it is 

 only in the larger specimens that the ventral fin rays are well developed. 



The caudal fin is here well marked off from the dorsal and ventral fins, there being 

 a well marked supra- and infra-caudal lobe in both specimens (figs. 11 and 13). 

 There are about 35 to 40 oral cirri of the usual type, bearing sense-papillse. On 

 the whole it seems fairly certain that these two specimens belong to the species 

 Branchiostoma indicum. The distribution also favours this conclusion, for the Orissa 

 Coast of India, where the species was found, is not far north of Ceylon. 



Branchiostoma californiense (?), J. G. Cooper. Plate I., figs. 14, 15. 

 (?) B. capense, Gilchrist. 



There is one specimen, No. V., Table IV., in the collection the identity of which is a 

 little uncertain. I refer it, with some little hesitation, to Branchiostoma californiense, 

 J. Cooper. In another paper (10) I have expressed doubt as to the distinctness of 

 B. californiense and B. capense. Since then Professor Herdman has received from 

 Dr. Gilchrist eight well-preserved specimens of his B. capense, and has placed them 

 in my hands for examination. In these I find no trace of an eye-spot. The specimens 

 range from 51 to 63 niillims. in length, and the number of myotomes from 74 to 76. 

 The formula varies within 46 to 48, 18 or 19, 9 or 10 47, 19, 9 being the most 

 frequent form. There are 35 pairs of gonads. This formula is so close to that of 

 B. californiense, and the two agree so well in proportions and characters of the head, 

 that notwithstanding the absence of an eye-spot I should hesitate to consider the 

 Cape form distinct until further specimens of the Californian species have been 

 examined. 



The Ceylon specimen was taken in the Cheval district (Stn. XL), at 6 fathoms, on 

 February 4th, and was 42 niillims. long. It had no gonads and was evidently 

 immature. Its myotome formula was 40, 20, 12 total, 72. 



The rostral fin is separated from the dorsal fin by a shallow notch. The dorsal fin 

 is low, and has a series of fin rays. The caudal fin is very slightly marked off from 

 the ventral and dorsal fins and has its infra-caudal lobe slightly the larger and deeper. 

 The ventral fin is very long indeed, and has a series of double fin rays running its 

 whole length. Neither the ventral fin rays nor chambers are prolonged postanally. 

 The metapleura have a symmetrical termination, thus determining the genus to 

 which the specimen belongs. 



