2 Dr. J. C. Melvill on Marine Mollusca 



finished — to properly examine these gatherings, a fact which 

 is not surprising- when the microscopic size of the bulk of the 

 material is considered. 



As is almost invariably the case in deep-sea products, the 

 predominating molluscan families are Pleurotomklac, first in 

 point of numbers, followed by Pyramidellidse, Trochidae, 

 Rissoidae, and Cerithidae. 



In the following descriptive paper I have eliminated all 

 members of the second family named — Pyramidellidae, — as I 

 have prepared, separately, a revision of the Gulf species, 

 which I hope may be published this autumn; but examples 

 of the remaining and other families will be found among the 

 twenty-nine species now to be enumerated. 



The time does not seem to have arrived for a new edition 

 of the ' Catalogue of Gastropoda and Scaphopoda ' published 

 in 1901, though a considerable number of species could now 

 be added, and several emendations would likewise have to be 

 made at the same time. 



Including the Pelecypoda, the catalogue of which was 

 published only three years ago, the number of Mollusca 

 enumerated from these seas amounts to over 1700 species, and 

 of these it has been found necessary to describe more than a 

 third as new to science. 



Acknowledgments are due to Mr. G. B. Sowerby, Mr. E. 

 R. Sykes, Mr. J. E. le Brockton Tomlin, and Mr. Edgar 

 Smith, I.S.O., while our sense of indebtedness to Mr. F. W. 

 Townsend has been, if possible, still further accentuated and 

 enhanced by the fresh services he has rendered to the science 

 of malacology during the past two years. 



Cychstrema tredecimUneatum, sp. n. (PI. I. rig. 1.) 



C. testa deprosso-discoidali, minuta, alba, delicata, late umbilicata ; 

 anfractibus 4, quorum 1| apicales mamillati, laeves, nitidi, 

 ceteris ad suturas leniter quasi-canaliculatis, penulfcioio spiraliter 

 3-, ultimo 13-lineato — supra sex, intra septem lineis praedito, — 

 liris indistinctis, hie illic fortioribus ; apertura obliqua, peristo- 

 mate rotundo, continue 



Alt. 1, diam. 2 mm. 



Bab. Gulf of Oman, kit. 26° 6' N., long. 50° 58' E., 15 

 fathoms. 



A rare and delicate species, white, discoidally depressed, 

 with large umbilicus, four-wborled, two being apical, mamil- 

 late, the remainder ornamented with fine, somewhat indistinct 

 and unequal spiral lines, thirteen in all upon the body-whorl, 

 six being on the upper side, and seven basal, round the 

 umbilicus. The periphery is not conspicuously angled. 



