180 THE VOYAGE OF H.M.S. CHALLENGER. 



the valves, aud the form of tlic specimen figured by Reeve as Lucina obliqua is exactly 

 that of the sheU figured by Philippi. 



Only a few small valves about 4 millimetres in length were dredged off Bermuda. 

 At this young stage they are q^uite as convex as the adult form, from which they differ 

 in ha\'ing the margin of the valves crenulated within. The outline and hinge characters 

 are about the same. 



Lucina (CodaMa) seminula, Gould (PI. XIII. figs. 5-5a). 



Lucina (Myrtea) seminula, Gould, Proc. Bostou Sac. Nat. Hist., 1861, vol. viii. p. 36; Otia 

 ConeL, p. 174. 



Testa minuta, crassiuscula, paulo obliqua, mediocriter convexa, irregulariter rotundata, 

 ante umbones excavata, alba. Valvse aliquanto insequilaterales, impressione radianti 

 utrinque notatae, costellis concentricis suljvalidis aliisque minoribus in interstitiis 

 instructse. Margo dorsi anticus prope umbones conspicue concavus, posticus declivis, 

 rectiusculus ; margo inferior excurvatus, ad latera leviter sinuatus. Lunula parva, 

 profundissima. Cardo validus. Dentes cardinales duo divergentes in valva sinistra, 

 unicus in dextra. Laterales breves, crassi, ab umbonibus sequidistantes. Pagina interna 

 minute rugulosa, ad marginem incrassatum fortiter dentata. 



This minute form is rather solid in texture, slightly oblique in outline, irregularly 

 rounded, concave in front of the umbones, straightish but oblique on the hinder dorsal 

 side. It is white, rather inequilateral, with a shallow radiating depression down each 

 side of the valves, which cause the lateral margins to be somewhat truncate or even 

 sinuated. The posterior of these is usually more pronounced than that in front. The 

 sculpture consists of twenty to thirty rather stout and elevated concentric costae, which 

 gradually become thicker as the shell enlarges, and attenuate at the sides. In the 

 interstices between them are numerous but more slender radiating lirse, which do not, 

 however, cross the others. The lunule, although small, is remarkably deeply excavated 

 beneath the overcurving umljones, each of which is smooth at the bluntish tip. The hinge- 

 plate is strong. There are two primary teeth in the left valve and one in the right, the 

 latter falling between the former, which are divergent. The laterals are strong, short, 

 erect, and about equidistant from the cardinals. The ligament is long, narrow, external, 

 in a groove on the posterior margin just behind the umbones. Tlie interior of the valves 

 under the microscope appears to be minutely rugose. The thickened outer margin is 

 coarsely denticulated, the teeth upon the front and lower margins being a little stronger 

 than those upon the posterior edge, where at times they are more or less obsolete. The 

 pallial line is simple and the muscular scars rather large. 



Length 2-|- mm., height 2 J, diameter If. 



