Bay of Bengal and the Arabian Sea. 161 



respects. It differs in having a thicker stouter spire, a shorter 

 canal, a thicker girdle at the top of the whorls, and a broader 

 tuberculated zone around the middle. 



The specimens obtained off the west of Ceylon are peculiar 

 for a kind of nodule or swelling on the upper part of the 

 columella. They are rather smaller, although full-grown, 

 than the examples from the Bay of Bengal. 



Of the two specimens examined one is 45 millim. in length, 

 the other only 40. 



6. Pleurotoma (Surcula) symbiotes, W.-M. & A. 

 (PI. III. figs. 7, 8.) 



Pleurotoma symbiotes, Wood-Mason and Alcock, Ann. & Mag. Nat. 

 Hist. 1891, vol. viii. p. 444, figs. 13 a, b. 



Testa fusiformis, sordide albida, epiderraide tenuissima pallide 

 olivacea hie illic induta ; anfractus 10, superne concavi, in medio 

 nodosi, striis spiralibus lineisque incrementi tenuibus flexuosis 

 sculpti, sutura leviter undulata sejuncti, ultimus antice angus- 

 tatus ; apertura intus fuscescens, lsevis, longit. totius k paulo 

 brevior; labrum in medio prominens, valde arcuatum, superne 

 late sinuatum ; columella lsevis, callo tenui pallide fuscescente 

 induta, in medio parum arcuata, inferne obliqua ; canalis 

 anterior latus, paulo recurvus. 



Longit. 57 millim., diam. 19 ; aportura cum canali 27 longa, 

 9 lata. 



Hab. Off southern extremity of India, lat. 7° 04' N., long. 

 76° 34' 15'' E., in 1043 fathoms. 



The nodules upon the central portion of the whorls (about 

 twelve in number on the penultimate) become gradually more 

 and more acute towards the top of the spire, where the suture 

 also is more wavy than lower down the shell, becoming quite 

 even in the last volution. The sinus in the outer lip, although 

 wide, is not deep, and is situated in the depression or con- 

 cavity below the suture. Neither the spiral lines nor the 

 acuteness of the nodules upon the upper whorls are well 

 shown in the figures referred to. 



7. Pleurotoma (Surcula) subcorpulenta. 

 (PI. III. fig. 6.) 



Testa S. symbioti similis, sed major, anfractibus supra minus exca- 

 vatis, striisque spiralibus paulo prominentioribus, columella in 

 medio plica obliqua plus minus prominente instructa. 



Longit. 80 millim., diam. 29 ; apertura 42 longa, 16 lata. 



Hab. Off Colombo, Ceylon, lat. 6° 32' N., long. 79° 37' E., 

 in 675 fathoms. 



