76 AMERICAN JOURNAL 



A full resume" of the synonymy, and a rectification of the same, 

 will be found in the Report before alluded to. Carelessness in 

 the identification of types and the neglect into which this and 

 the last family have fallen, are the probable causes of the con- 

 fusion which has hitherto pervaded them. These rectifications 

 will perhaps meet with some opposition from those naturalists 

 who forget that accuracy is the basis and aim of all Science. 

 There can be no doubt as to the true type of this genus, and 

 that it is as distinct from the forms which have been usually 

 regarded as typical Distrince on the one hand, as Orbiculoidea is 

 on the other. 



The following are the recent species. Those marked with an 

 ! I have personally examined. 



Diseina striata ! Dall ex Schum. 1. c. 

 Habitat. North west coast of Africa. 



Diseinisca stella! Gould, Proc. Bost. Soc. Nat. Hist, vii, p. 

 323, Sept. 1860, Rve. Conch. Icon. PI. 1, fig. I, 1862. 

 Singapore and Philippines, Cuming. China Seas, Stimpson. 



Diseinisca lamellosa ! Brod. P. Z. S., 1833, p. 124. Rve. 

 Conch. Icon. PI. 2, f. 3, 1862. 

 Panama to Peru. 



This is the subgeneric type. I have examined an immense 

 number of specimens from Panama and find that they exhibit 

 many varieties. This species has no radiating striae and is a 

 thinner shell than D. la>vis. 



Diseinisca tenuis, Sowerby, Thes. Conch, i, p. 366, PI. 73, f« 

 4—5, 1847. Not of Reeve, Conch. Icon. PI. 1, f. 5, 

 1862. 



Habitat f 



Reeve's figures of Orbicula tenuis do not represent Sowerby's 

 species, but agree well with some of the varieties of D. lamellosa. 

 I have seen no specimens of either, but the figures exhibit dis- 

 crepancies too great to be reconciled. Sowerby gives no locali- 

 ties, and Reeve's localities, or one of them, probably refer to the 

 form which he figures. It can hardly be found both in Chili and 

 South Australia, and the double habitat is probably due to an 

 error in labelling or identification. 



Diseinisca Icevis ! Sby., Trans. Lin. Soc. xiii, p. 468, PI. xxvi, 

 f. ], a— d, 1822. Reeve, Conch. Icon. PI. i, f. 4, a-b, 

 1862. 



Concepcin, Chili, Cuming. 



