336 PALEONTOLOGY OF ILLINOIS. 



Leiodus calcarattts, St. J. and W. 



PL YIT, Fig. 11-18. 



Teeth variable in size and form, and separable into three or four 

 varieties, which, however, are not persistent, blending into each other 

 by almost imperceptible gradations, but which may be distinguished 

 under three heads, (posterior, median and anterior teeth,) according to 

 their supposed position upon the jaws. Of these the median teeth are 

 the largest, presenting a massive build and a somewhat strongly arched 

 outline; base as long, and more or less oblique to, the crown, deep, 

 thick, angular in outline, deeply channeled on one side, with a more or 

 less angular convexity occupying the opposite side, both sides coarsely 

 roughened and vernacularly pitted, inferior surface smooth, and 

 obliquely beveled to an edge along the inner margin ; crown generally 

 strongly arched vertically, sharply constricted basally, risiug into a 

 more or less tumid, eccentric prominence, which is more or less pro- 

 duced inferiorly in the outer margin, surmounted by a slightly recurved 

 acute apex ; lateral wings gradually narrowed towards the extremi- 

 ties, which are obliquely truncated or rounded, and usually slightly 

 curved forward, more or less undulated along the margins, with an 

 obscurely defined median crest, surfaces nearly equally and regularly 

 convex vertically, obscurely and irregularly lobed, with one to three or 

 four narrow vertical sulci in one or other extremity, giving rise to an 

 annulated appearance and faint secondary cones in the crest; basal 

 margins marked by more or less numerous, faint ruga? — otherwise the 

 coronal surfaces are smooth and finely punctate. From individuals 

 possessing the above characteristics there seems to be a gradation into 

 smaller forms, some of which are of minute size, and which are readily 

 recognizable by the extremely produced, slender, eccentric cone, which 

 latter is also more or less deflected laterally, as well as recurved, more 

 strongly produced basally in front, and seldom, if ever, lobed, though in 

 in the larger individuals the lateral extremities are faintly uudnlated ver- 

 tically, in the smaller ones laterally abbreviated, and the apex less eccen- 

 trically produced ; in other respects presenting a community of characters 

 which intimately connect them with the larger teeth. A third form, 

 ^which may have formed the posterior rows, is represented by individuals 

 differing in no respect from the median teeth, except in the truncated 

 or obtuse cone and depressed lateral wings. A fourth and sparsely 

 represented variety is distinguished by the rather elevated, sharp- 

 pointed, antero-posteriorly compressed crown. Coronal surfaces envel- 

 oped iu a thin, polished enamel-like layer, and very faintly verrucose; 

 in worn surfaces the punctate structure is much more distinct, and iu 

 immature teeth the crown presents an elegant verrucose or roughened 



