125 
dentibus subundulatis ; dentibus cardinalibus anticis in valva 
sinistra superficialiter bisulcatis, tertio pertenui, dente medio in 
valva dextra cuneato, e lamellis duabus complicatis composito, 
tertio curvato, profunde diviso ; margine interno dense et fortiter 
dentato. 
Long. 38, alt. 37°5, crass. 21 mill. 
Hab. Japan. 
Var. Testa tumidiore, zonis flavidis prevalentibus, liris transversis 
infra remotioribus, lineis longitudinalibus medio obsoletis. 
Hab. China. 
This species is easily known by its being nearly equilateral and 
well-rounded, and by the fine impressed lines running from the apex 
to the base, which are scarcely visible in the middle, but grow 
stronger at the sides, particularly at the hinder part of the shell, 
where they show a pale cerulean colour. The regular and close-set 
transverse striee produce a kind of silky appearance, which, in con- 
nexion with the pale bluish and yellowish bands, gives the shell a 
very agreeable aspect. There are peculiarities of the pallial sinus 
and of the hinge which also distinguish this species from all its con- 
geners. 
13. CycLinaA PECTUNCULUS, Romer. C. testa orbiculari, vix 
altiore quam longa, antice rotundatim productiore, ad marginem 
basalem posticum vie dependente, lentiformi, valde tumida, soli- 
diuscula, attamen diaphana, modice inequilaterali ; umbonum re- 
gione transversim tenuissime striata, striis marginem ventralem 
versus crassioribus, et infra in liris rotundatis, irregularibus, 
mutatis; albida, irregulariter ferrugineo maculata et punctata, 
superficie subnitente ; umbonibus tumidis, valde prominulis, oblique 
incurvis, contiguis, in 2 longitudinis collocatis ; area lunulaque 
nullis, ligamento late conspicuo ; intus lactea, nitida ; sinu palliari 
mediocri, sublate aperto, apice expanso, subrotundato, lineis sub- 
rectis incluso ; lamina cardinali lata, dentibus cardinalibus validis, 
- medio in valva dextra cuneiformi, subacuto, tertio crasso, oblique 
producto superficialiter bisulcato ; margine interno dense denticu- 
lato. 
Long. 39, alt. 40, crass. 26 mill. 
Hab. China. 
Among the little varied forms presented by the genus Cyelina, the 
species described is remarkable for the elevation of its umbones and 
the produced dependent hinder part of its basal margin. It is there- 
fore not unlike in shape to a Pectunculus, and I know only one species 
in my own collection, and named by me Cyclina intumescens, with 
which it can be compared. Near the umbones the surface is covered 
with very fine transverse lines, which become stronger by degrees 
and finally change into rude, irregular, thick-set stri. Although 
the valves are tolerably solid, yet they are prettily transparent, and 
produce at the inner part a china-like lustre. C. intumescens is a 
thicker and more oblique shell, of a rounded quadrangular outline, 
presenting fine longitudinal lines. 
