186 PALAEONTOLOGY OF ILLINOIS. 



Geological position and localities: Upper Burlington fish-bed ; Bur- 

 lington, Pleasant Grove, Augusta, Buffington creek, Louisa county, 

 (Iowa) ; Honey creek, Henderson county, (111.) The mandibular 

 median teeth especially alluded to above are amongst the beautiful 

 collections from the Buffington creek locality, belonging to Mr. 

 Springer. 



SANDALODUS L^VISSIMUS, N. and W. 



PI. XII, Fig. 8, 9. 



Sandalodus Icevissimus NEWBEEBY and WOETHEN, 1866, III. Geol. Surv., II, p. 104, PL 10, 

 f. 6, 7, 8. 



Sandalodus grandis, NEWBEBEY and WOETHEN, ib., II, p. 105, PI. 10, f. 9. 

 Deltodus grandis, NEWBEBEY and WOETHEN, ib., II, p. 101, PL IX, f. 9, 9a. 

 Cochliodus ? crassus, NEWBEEEY and WOETHEN, ib., II, p. 91, PL VIII, f. 2,-2a. 

 Psammodus ? seml-cylindricus, NEWBEBBY and WOBTHEN, ib., II, p. 109, PL XI, f. 4, 4a. 

 Psammodus ? rhomboideus, NEWBEEBY and WOETHEN, ib., II. p. 110, PL XI. f. C, 6a. 



Mandibular median (?) teeth attaining large size, triangular in 

 outline, strongly arched longitudinally with strong spiral inrollment 

 of outer extremity, lateral borders diverging at an angle of about 50. 

 Postero-lateral border making an angle of about 30 with the inner 

 margin, very gently curved in its course, coronal enamel forming a 

 narrow fold strongly inbeveled to the channeled basal portion, which 

 is rounded below into the inferior surface of the tooth; antero- 

 lateral border considerably shorter and slightly concave in its 

 course, thick articular edge not shown ; inner margin very gently 

 and regularly arched between the subacute anterior and posterior 

 angles, inbeveled below. 



Coronal region presenting a uniform plane surface transversely, 

 with a slight convexity near to and parallel with the postero-lateral 

 border, interrupted toward inner margin by irregularly disposed 

 transverse undulations, or lines of growth, and faint longitudinal 

 lines, sometimes appearing as narrow impressed sulci. Surface 

 punctation minute and crowded, along the inner margin concealed 

 beneath the dense enamel layer. The punctate structure bears 

 closest agreement with that observed in the large posterior forms of 

 Sandalodus Icevissimus. A large-size tooth measures across the inner 

 margin 50 mm. ; length along postero-lateral border to point of in- 

 rollment, 47 mm. ; ditto, along the antero-lateral border, about 

 30 mm. 



