Mr. W. Clark on British Mollusca. 413 



I hope I have succeeded in rescuing the T. atomus of the excellent 

 Philippi from being supplanted by Mr. Jeffreys in consequence of 

 his fanciful idea that, because it is discoid, flat above, and umbilicated 

 beneath, it must be the last living representative of the fossil Euom- 

 phali. These are the only data given for a substitution which I 

 must consider destitute of foundation. 



I shall now terminate this rapid sketch of some of the notices in 

 the "Gleanings" by giving an account of the Cheinnitzice, which are 

 generally termed by Air. Jeffreys Odostomice, and are largely men- 

 tioned in them, and have been kept back for the convenience of 

 considering them in a collective form. 



These Pyramidellidan genera and species, though they have been 

 more sedulously looked after than any other division by the British 

 naturalist, are in a confused and unsatisfactory position, resulting 

 from the constant endeavour of conchologists to constitute species 

 from the almost imperceptible differences in the form and contour of 

 these minute objects, without considering, in the genera I have men- 

 tioned, the excessive versatility of the variations of their species, 

 Mr. Jeffreys, at our late conference, gave me some specimen-types of 

 his own constituted species, and afforded me the opj)ortunitv of in- 

 specting the remainder, of which examples could not be spared. The 

 result of a searching examination and comparison with my own ex- 

 amples has satisfied me that his own peculiar species, O. alba, O. al- 

 bella, O. dubia, O. rissoides, and O. Lukisii, are only diminutive sub- 

 varieties of a singular dwarf variety of my Chemnitzia imllida, which 

 is the O. euUinoides of some authors, and by far the most variable 

 species of the genus, — indeed so much so, that it is difficult to find 

 two similar examples ; even Mr. Jeffreys has appended to it five va- 

 rieties, a, b, c, d, e, in his paper in the 'Annals,' 2ndser. vol.ii. p.335. 

 I have compared the animal of this new dwarf variety with the typical 

 Cliem. pallida, and found it identical, both in respect to the organs, 

 and the operculum, which latter appendage differs from that of 

 every other Chemnitzia ; and, with the reservation of the incidents that 

 may arise from a re-examination, I propose to name it Chem. pallida 

 var. nana et protea, as, out of my very numerous suite, more than half 

 are of such dissimilar forms, that they might constitute species with 

 more justice than many that figure in our books. This protean squa- 

 dron is the littoral phase of the Chem. pallida, and if e^er found at sea 

 in deep water, has been transferred thither by the tides and currents. 

 I hope this summer to be enabled to remodel the Chemnitzice, so 

 that collectors may easily identify these objects, which now puzzle 

 them so much, that Mr. Jeffreys wrote me word that he has had hun- 

 dreds of shells of these genera and species sent him to name and 

 identify. What does this prove, but that the characters are so slight 

 and superficial as to defy discrimination ? It will be asked, may not 

 the animals I consider as varieties live with the dwarf variety of the 

 "• pallida'" as species? I answer, the differences are too partial and 



meshes large enough to let tliera pass through, when the Algae are moved 

 about carefully, into another very fine sieve placed under the first, from 

 which they may be collected by the aid of a lens and a camel's-hair brush. 



