By measurement with a goniometer attached to a compound microscope, the plane angle between the lines of cross cleavage, or _cl_, and the edge _I_:_I_ (which equals the inclination of _O_ on the orthodiagonal section, or a plane _ii_) was found to be 117-117½°; and that between edge _I_:_I_ and edge l:l (which equals _ii_ on l_i_, both unobserved planes) 95°-95½°: whence _O_:l_i_ would equal approximately 147° 30’. The inclination of the rough plane _r_ on the edge l:l is about 110°, but varies much. The results of calculation, taking as data the above mentioned angles _I_:_I_ and l:_ii_, along with the inclination of _O_ to _ii_ = 117° 15’, and that of the edge l:l (or l_ì_) to _ii_ = 95° 15’ are as follows: C (= O : _iì_) = 117° 15’ and 62° 45’ _a_ (vert. axis) : _O_ (clinodiag.) : _c_ = 0.5396 : 1 : 2.614 l : l = 156° 46’ -l : -l (unobserved planes) = 164° 22’ The species is related in form to Vivianite, in which _a_ : _b_ : 2_c_ = 1.0792 : 1 : 2.614. The crystals of the two species are also alike in the perfect and pearly clinodiagonal cleavage. On new Californian Marine Shells. No. II. BY PHILIP P. CARPENTER, PH. D., OF WARRINGTON, ENGLAND. Genus COLLONIA, _Gray_, 1852. This genus was established (in English) by Dr. Gray, for Turbinate shells having an “operculum circular, with many gradually enlarged whirls, with a convex external rib and central pit.” The type (still appearing as such in the B. M. Col.) is a smooth fossil from Grignon, = Delphinula marginata, Lam., with a keeled and crenated umbilicus, like Phillippia. Another (African) shell is joined to the diagnosis, with the following brief description: “C. striata, _Gray_. Shell red, white marbled, striated.” It is quoted by Phillippi, Handb. Conch. p. 206, who assigns as a type T. sanguineus, _Linn._ For this species and its congeners, we now propose a subgenus LEPTONYX, as they do not agree with the type. The genus was reconstituted by Messrs. Adams, Gen. i. 396 for shells with “imperforate axis and contracted aperture:” the description of the operculum being copied from Gray. The type is now “C. marginata, _Nutt._” pl. 44, f. 2, the operculum of which is figured as with _few_ whirls. The same description and figure are given in Chenu, Manuel i. 348, f. 2560. The error seems to have arisen thus. Mr. H. Adams (who acted for the ‘firm’ during his brother’s long absence in Japan,) probably took Gray’s C. marginata to be the ‘Turbo marginatus, Nutt.’ of Reeve, and from this species as type, described the genus to be imperforate, etc. Unfortunately, Dr. Gray did not observe the error, which had arisen from confounding two different shells called marginatus; and in his guide to Mollusca (in loco) he adopts the description of Messrs. Adams; so that