Mr. 11. Adams on a new Genus of Land- Shells. 177 



XX. — Description of a new Genus of Land- Shells from the Island 

 of Labuan, Borneo, By Henry Adams, F.L S. 



Genus Plectostoma, H. Adams. 



Testa conica, umbilicata ; anfractus ultimus solutus, protractus, 

 sursum flectus, iade retrorsum extensus ; apertura simplex ; peri- 

 stoma subverticale, expansum. 



Plectostoma DeCrespignii, H. Adams. 



P. testa elevato-conica, tenuissima, pallido-fulva, laminis numerosis 

 longitudinalibus tenuibus erectis munita, sutura valde impressa, 

 apice subacute ; anfractibus 6, eonvexis, ultimo tubam protractam, 

 postice paulum eonstrictam, sursum flectam, inde revertam effor- 

 mante ; umbilico aperto ; apertura circulari, subverticali, paulu- 

 lum reclinante ; peristomate libero, valde expanso, reflexiusculo. 



Diam. major 2, minor 1^, axis 2 mill. 



Hab. Labuan Island, Borneo. 



This minute but very interesting species of the family Heli- 

 cidse was found by Mr. De Crespigny, after whom I have named 

 it, in the island of Labuan, Borneo. It appears to have affinities 

 both with the genus Boysia, Pfr., and Hypselostoma, Bens., from 

 which, however, it diiFers in having the last whorl constricted at 

 its separation from the others, and in the extraordinary pro- 

 longation backwards of the free portion. From Boysia it also 

 differs in being more Heliciform, and in having the umbdicus 

 open ; and from Hypselostoma in the aperture being edentulate. 



XXI. — Diagnoses of new Forms of Mollusca from the West Coast 

 of North America, first collected by Col. E. Jewett. By Philip 

 P. Carpenter, B.A., Ph.D. 



An account of Col. Jewett's shells will be found in the British 

 Association Reports for 1856 (pp. 226-231) and 1863 (pp. 534- 

 539). The exact localities are often uncertain; but many of 

 them have been fixed by subsequent explorers. Being generally 

 worn beach-specimens, the diagnoses have been written (where- 

 ever practicable) from perfect shells, and especially from the 

 beautiful series dredged by Dr. J. G. Cooper, in the Californian 

 State Survey. The types belong to Mrs. Boyce, of Utica,N.Y., 

 and are at present in my keeping. The numbers, in the species 

 from the temperate fauna, refer to the table in the British Asso- 

 ciation Report for 1863, pp. 636-664. 



37 b. Solen (? sicarius, var.) rosaceus. 

 S. testa S. sicario simili, sed minore ; multo angustiore, elongata, 

 Ann. §• Mag, N. Hist. Ser. 3. Vol xv. 12 



