Bay of Bengal and the Arabian Sea. 171 



umbonem valvaa dextrce brevis, prominulus ; valva sinistra eden- 

 tula ; fossa ligameuti minima, triangularis. 

 Longit. 16 millim., alt. 9*5, diam. 7*3. 



Hob. Bay of Bengal, lat. 6° 29' N., long. 29° 34' E., in 

 597 fathoms. (The longitude should probably be 92° not 29°.) 



The prominent characteristics of this species are its form, 

 the oblique truncation of the anterior end being peculiar, and 

 the four prominent keels upon the hinder half of the valves. 

 The right valve is a trifle smaller than the left, and this is 

 most noticeable at the posterior end when the valves are 

 closed. The inner surface exhibits grooves corresponding to 

 the external costas, which, being produced at the extremities, 

 give to the ventral margin a festooned appearance. 



Named in honour of Dr. A. Alcock of the ' Investigator.' 



26. Lucina bengalensis. (PI. V. figs. 1, 2.) 



Testa mediocriter tenuis, irregulariter rotundata, paulo inosquilate- 

 ralis, antice brevior ; valvas parum convexoe, cretacea?, epidermide 

 tenui grisea indutse, lamellis concentricis tenuissimis striisque 

 interjectis ornatse, lunula lanccolata instructae ; margo dorsi 

 posticus leviter arcuatus et declivis, anticus infra umbones paulo 

 excavatus ; ventris margo valde curvatus ; dentes cardinales duo 

 in utraque valva imequales, divergeiites, lateralis unicus anticus 

 inconspicuus ; pagina interna alba, minute subasperata ; cicatrix 

 antica elongata, angustissima, postica ovata. 



Longit. 37 millim., alt. 31, diam. 13. 



Bab. Off the delta of the Godaveri, lat. 16° 01' N., long. 

 81° 25' E., in 410 fathoms. 



This species agrees very closely, excepting in form, with 

 L. lamellata, Smith *, from the Straits of Magellan. The 

 concentric lamellse, however, are perhaps a trifle finer and 

 closer together, and the anterior adductor scar is narrower. 



27. Ltmopsis indica. (PI. V. fig. 7.) 

 Testa insequilateralis, crassiuscula, valde oblique ovata, antice 

 arcuata, postice oblique subtruncata, alba, epidermide olivaceo- 

 fusca hirsuta amicta, striis numerosis radiantibus aliisque concen- 

 tricis decussata ; umbones parvi, acuti ; area ligamenti pro- 

 funda, excavata, ligamento parvo mediano rhombif ormi instructa ; 

 dentes cardinales circiter 14 in utraque valva ; pagina interna alba, 

 radiatim tenuissime striata, margine externo crasso piano circum- 

 data. 

 Longit. 20 millim., alt. 18, diam. 9. 

 Exemplum alterum 17 longa, 16 alta, 10 crassa. 



Hob. Colombo Lighthouse, S. 64° E. 13^ miles, in 142- 

 400 fathoms. 



* Report Lamellibranchiata ' Challenger,' p. 173, pi. xiii. figs. 1-1 b. 



