430 A MANUAL OF AMERICAN LAl^^D SHELLS. 



aptM-lure lunate-oval, subaiigulated ', peristome straight, acute, its mar- 

 gins joiued by an entering callus. 



But very_few species of this genus are known, restricted to Cuba and 

 Hayti. One of them has, however, been quoted from Guiana, and an- 

 other has become naturalized in our Florida Subregion, having been 

 introduced into the southern extremity of the j)cniusula. 



Jaw thick, arcuate, cuds rapidly attenuated, pointed ; composite, be- 

 F1G.47-. ing in numerous, separate, free, imbricated, triangu- 



^^^;^Xf',/r>>>. lar pieces, with sutures inclined obliquely to the 

 ^'^^''^^^^^^^^^ center of the jaw, so as to leave an upper median 

 Jaw of i. ruv/incws. angular i^iece; other pieces are soldered together 

 above. Cuttiug edge with no median projection, serrated by the lower 

 angles of the oblique pieces. For more detailed description see below, 

 under Orthallcus, which has a similar jaw. I am not able to give a figure 

 of the jaw of the only species found within our limits, L.fasciatus.* It 

 is, however, figured by Leidy (Vol. I, Plate V,.Fig. 4, a, h). It is sim- 

 ilar to that of the allied species, L. virgineus, which is figured here. 



The only species found within our limits, L. fasciatus, has about 69- 

 1-69 teeth, judging from a lingual membrane examined by me. That 

 figured in L. and Fr.-W. Sh., I, p. 214, has 94 rows of 55-1-55 teeth 

 each. As elsewhere stated, there is often a diflerence in the number 

 of transverse teeth in almost all species, and indeed upon different 

 parts of the same membrane. The membrane is shaped like that of 

 Orthalicus. (See Terr Moll., V, Plate XVI, Fig. M.) 



The central tooth (Terr. Moll., V, Plate X, Fig. G) has a base of at- 

 tachment long and narrow, with strongly incurved sides, widely ex- 

 panded, excurved, and fringed lower margin, and upper margin less 

 expanded, rounded, and broadly reflected. The reflection is stout, and 

 very rapidly narrows, without any appearance of side cusps, into a 

 very broad, loug, bluntly rounded median cusp, bearing a still broader, 

 short, bluntly truncated cutting edge (as such a blunt organ cannot be 

 called a point), reaching nearly to the lower edge of the base of attach- 

 ment. It may be that Ihave here incorrectly considered the upper 

 margin of the base of attachment as reflected and extended into the 

 cusp. As in the case of the side teeth, I should, perhaps, rather say 

 that the upper margin is not reflected, but that just below the middle 

 of the base of attachment there springs up from its surface a broad, 



* Specimens lately collected by Mr. Hemphill have furnished me \^■ith the jaw. 

 These are ouenpper, triangular, median i^late and six plates on either side of this. 



