174 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



{pars), H, & A. Adams, 1854 {M. aciiticarinata (error for aciito- 

 carinata), Lea = ^. Jlrf/micwn, Gmel.) ; Melasma, H. & A. 

 Adams, 1854 {Ilelania blanda, Lea = £. Vm/inicinn, Gmel.); 

 Ju(/a,J^. & A. Adams, 1854 {JJ. Virf/inicwn, Gmel.); Tryphanostoma 

 (sp.), Lea, 1862 (T. Kmxvillense, Lea = B. Virginicmn, Gmel.); 

 Goiiiobasis (h]).), Lea, 1862 {G.Draytonii, Lea = M./plicifera, Lea). 

 Type, Buccinum Virginicum, Gmelin. 



Shell of moderate size, avera<>ing' 25 mm. in altitude, sub-solid, 

 spire attenuate, whorls normally barely rounded or slightly incurved 

 between the suture and the rounded periphery, aperture simple, the 

 ])illar curved and imperforate, outer lip sinuate and somewhat 

 produced below; habitat lakes and streams, occupying a wider 

 variety of situations than any other genus in this family. 



Amhloxus includes the fusiform Pleurocerids, the last genus of the 

 family to he definitely separated from the Lamarckian Ilelania, and 

 hence one which has suffered considerable nomenclatural vicissitude. 

 None of the species are known to have specialized up to the stage 

 corresponding to lo in the preceding genus, or Gyrotoma, s.s., in the 

 one to follow. The members of this group are very similar, and not 

 always easy to separate, but with the exception of the Eocene tenerus 

 and the recent Virginicus all seem sufficiently distinct. Normally 

 each is smooth, hut malleated, axially plicate, suturally carinate, 

 peripherally carinate, multicarinate, and spirally frilled forms or 

 types embodying a combination of two or more of these characters 

 apparently occur in every species. These are unquestionably of the 

 nature of syntonic modifications, but, in contrast to other groups so 

 aifected, the early growth appears to he the most frequently and 

 seriously deformed, the distortion prevailing in the adult condition 

 only in extreme instances. The philosophy of this is not entirely 

 understood, but it is probable that the stage preceding the present 

 adult stage was a sculptured one, and certain atavistic tendencies are 

 so influenced that the shell assumes bizarre forms. 



The synonj'my of A. Virginiais in spite of its length has been 

 given in full in order to suggest the vast multiplicity of forms that 

 may be expected in a rampantly susceptible species, distributed over 

 a wide area and naturally exposed to many influences. While 

 ])robably by no meails complete, it is yet a striking testimonial of 

 how the American Melanoids should not be classified. Since the 

 bulk of the synonyms are based on syntonic forms, for brevity a few 

 of the better-known normal forms are so noted. 



Ambloxus Virginicus (Gmelin). 

 Buccmum Virginicum, Gmelin, 1788 (normal); 21elania carinifera, 

 Lamarck, 1801 ; M. elerata, Say, 1821 ; M. multilineaia, Say, 

 1822; 11. catenaria, Say. 18i22; 31. pro.vima, Say, 1825; 

 M. simplex. Say, 1825; M. laqueata, Say, 1829; M. depygis, 

 Say, 1829; M. cancellata. Say, 1829; M. semicarinata, Say, 

 1829 ; 21. acuta, Lea, 1830 ; M. suhularis, Lea, 18o0 ; M. Uvescens, 

 ^Nfenke, 1830; 31. fasciata, Menke, 1830; 31. auriscalpinm, 

 Menke, 1830; 31. curia, Menke, 1830; 31. {Amhloxus) rugosa, 



