76 



organization of a multitude of extinct forms, filled by the hardest 

 matrix : and I have no doubt but that before very many years the 

 internal details of all the fossil species will be as well known as if they 

 were in the recent state. 



Much, however, remains to be done before the proposed classifi- 

 cations can be decidedly and definitely adopted, and many modifica- 

 tions will be considered requisite, as it is evident, from our present 

 knowledge, that some genera or sections are more or less closely re- 

 lated, and that certain species possess characters common to more 

 than one genus, but these examples are few and exceptional in com- 

 parison to those presenting a similar organization : thus all forms 

 with a free, simply attached loop, as in Ter. Australis, Ter. Califor- 

 niana, &c., must be placed in the same section ; all those with the 

 loop aiRxed to the hinge plate and to a central more or less elevated 

 septum, such as Ter, dorsata, Ter. rubicunda,&c., into another group ; 

 those also in which the calcareous appendages consist of only two cen- 

 tral diverging lamellae, such as Ter. rubra, Ter. pisum, and others, 

 must necessarily be placed close to each other, &c. The arrange- 

 ment of the species is, therefore, not a matter of indifference, but 

 ought to partake of those rules, followed for the other classes of Mol- 

 lusca, wherein genera are often admitted on far less important differ- 

 ences. 



A complete monograph of the recent species thus framed, with 

 figures, synonyms, dates, &c., is still a desideratum, and I hope ere 

 long that the science of Conchology will be enriched by such a valu- 

 able and necessary contribution. 



The only object of this short paper is to describe some unfigured 

 forms, to which I have added some remarks on a few species not 

 hitherto completely miderstood. 



1. Terebratula Grayii, Dav. 1852. (PI. XIV. fig. 1-3.) 



Biagnosis. — Shell irregularly pentagonal, rather broader than long; 

 valves unequally convex (the perforated being gibbous and the smaller 

 valve rather flattened) ; lieak not much produced, truncated by a very 

 large emarginate foramen — the deltidial plates are disunited, a small 

 portion of the aperture being completed by the umbo ; hinge-hne 

 straight; beak-ridges sharply defined, leaving between them and the 

 hinge-margin a vidde, almost flat area ; surface ornamented by a great 

 number of irregular and unequal radiating costse, augmenting rapidly 

 from numerous bifurcations and intercalations of smaller plaits be- 

 tween the larger costse ; colour partly yellow and red, this last be- 

 coming more vivid as it approaches the concentric lines of growth ; 

 structure punctate ; internal appendages consisting of a simply 

 attached loop, the riband-shaped lamella extending to about four- 

 fifths of the length of the shell before bending back on itself. Di- 

 mensions variable: length 14, width 15, depth 9 lines. 



Hab. Coast of Korea. Coll. Cuming. 



Obs. — This fine species has been known to me for several years, but 

 unobserved by other collectors, who erroneously supposed it to be 

 the Ter. rubra of Pallas, to which it bears some external resemblance. 



