172 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



Woodward, Recent and Fossil Shells, pi. vii, fig. 2 ; also Mon. Pal. 

 Soc, 1856, p. 200, pi. xxiv, figs, lla, lie. 



Conorbis, judging by the only test that can be applied to it, viz. 

 the conchological, almost runs into certain species that have been 

 assigned to the genus (or subgenus of Fleurotoma) Genota, H. & A. 

 Adams. 



The type, O. mitrceformis (Wood), a recent species from East 

 Indian seas, is not so akin as others more recently described by 

 Watson and Dall under the names Pleurotoma [Ge^iota) atractoides,^ 

 Watson, from the Philippines, and P. viahrunnea, Dall, collected in 

 the New World tropics during the " BLake " expedition. With these 

 should be associated Pleurotoma amphiconus, J. de C. Sowb., a fossil 

 shell of the closest relation to botli the species chiefly now under 

 discussion. Here the aperture is narrow and conoid, and it would not 

 be a matter of surprise to see some future palsEoutologist placing this 

 species in the same genus that was formed to include C. dormitor. 



It may not, indeed, be out of place to give two quotations by the 

 late Dr. Searles V. Wood & F. E. Edwards,^ in speaking of the 

 analogies and appearance of this species: "In the elevated conical 

 spire, the almost semicircular form of the outer lip, and the 

 produced base of the whorls, it presents the closest analogies with 

 that section of the Pleurotomm formed of P. prisca, amphiconus, 

 linearis, and similar species. Indeed, so closely does it approach to 

 some of them that, judging from external characters only, it is 

 difficult to decide to which genus it should be referred. The straight, 

 narrow aperture, however, is entirely that of a Cone, and indicates 

 a necessity that the animal, in order that it might withdraw into the 

 inner whorls, should be enabled to enlarge the space within the shell, 

 a necessity which was met by the power of absoi^ption possessed by 

 the animal. The curvature of the outer lip is all quite distinct in 

 its character from the sinus in the outer lip of the Pleurotomida.'^ 



And again : " In the well-known Eocene species,^ C. dormitor, 

 Sol., for instance, the shell outwardly possesses quite as much of the 

 character of a Pleurotoma as that of a Cone ; and Mr. Swainson has, 

 in fact, taken it as the type for a genus which he has named Conorbis, 

 and which, in his circle of affinities of the Conidce, he regards as the 

 representative of the Pleurotomidce. This division depends entirely 

 on the external characters of the shell ; no living representative has, 

 I believe, been found, and the animal is therefore unknown. It is 

 certain, however, that it was a true Cone, for, on breaking a specimen, 

 the inner whorls will be found reduced by absorption to a membrane-like 

 thinness, and the capability to effect this is not, I believe, possessed 

 by the animal of Pleurotoma. The proposed genus, Conorbis, is not 

 well defined by its author, and is not generally received, although 

 it may be adopted as a section of Conus. The characters appear to be 



1 Rep. Challenger Exped., Zoology, vol. xv, p. 301, pi. xx, fig. 8. 

 ' Mon. I'al. Soc, 1856, p. 301. 

 3 L.c, p. 118. 



