GLEN DEAN CONODONTS 



23 



mens of L. paradarki, the posterior bars of 

 both the holotype and figured paratype are 

 broken. In the Glen Dean specimens this 

 bar is twisted so that the denticles on it, 

 although normal to the bar, curve toward 

 the outer side of the fossil. Apparently 

 there is a typographical error in labeling 

 of Mass's figures 15 and 16 of plate 16 as 

 both views are labeled as showing the outer 

 side. Actually the greater expansion of the 

 base of the apical denticle is on the inner 

 side. 



Material studied. — 8 specimens. 



Distribution. — Glen Dean Formation of 

 Illinois, Indiana, and Kentucky, the Bar- 

 nett Formation of Texas. 



Repository. — Illinois State Geological 

 Survey, 3P56, 3P57 (figured specimens). 



Crenus Neoprioniodus Rhodes and Miiller, 

 1956 



Type species: Prioniodus conjunctus Gunnell 



Neoprioniodus camurus Rexroad 



Plate 5, figures 5 and 6 



Neoprioniodus cainurus Rexroad^ 1957, Illinois 

 Geol. Survey Rept. Inv. 199, p. 33, pi. 2, figs. 

 18-20. 



Some of the Glen Dean specimens of N. 

 camurus have as many as fifteen denticles 

 on the posterior bar. Complete specimens 

 show that the terminal fang is rather short, 

 tapering uniformly to a point. None of the 

 Glen Dean specimens have the relatively 

 thick posterior bar which was noted in four 

 specimens from the Renault and Paint 

 Creek Formations. 



Material studied. — 44 specimens from 

 this study, 20 from the Rexroad 1957 study. 



Distribution. — Renault, Golconda, Glen 

 Dean, Menard, and Kinkaid Formations of 

 Illinois, Indiana, and Kentucky. 



Repository. — Illinois State Geological 

 Survey, 3P58, 3P59 (figured specimens). 



Neoprioniodus loxus Rexroad 

 Plate 5, figures 7-9 



Neoprioniodus loxus Rexroad^ 1957, Illinois Geol. 



Survey Rept. Inv. 199, p. 34, pi. 2, figs. 8, 9, 14. 

 Neoprioniodus tenuis Rexroad, 1957, ibid., p. 35, pi. 



2, figs. 13, 16. 



A number of specimens intermediate be- 

 tween N. loxus and N. tenuis were found 

 in this study. The two extremes are read- 

 ily distinguishable on the basis of differ- 

 ences in cross-section shape of the posterior 

 bar. N. tenuis has a proportionately deeper 

 and thinner bar. However, the presence of 

 intermediate specimens gives a gradational 

 series between the two extremes, and it 

 seems best to place the two in synonomy. 



Material studied. — 49 specimens from 

 this study, 35 from the Rexroad 1957 study. 



Distribution. — Renault, Paint Creek, 

 Golconda, Glen Dean, and Menard For- 

 mations of Illinois, Indiana, and Kentucky. 



Repository. — Illinois State Geological 

 Survey 3P60, 3P61, 3P62 (figured speci- 

 mens). 



Neoprioniodus scitulus (Branson and 



Mehl) 



Plate 5, figures 10-14 



Prioniodus scitulus Branson and Mehl^ 1940, Deni- 

 son Univ. Bull., Jour. Sci. Labs., v. XXXV, p. 

 173, pi. V, figs. 5, 6; Cooper, 1947, Jour. Paleon- 

 tology, V. 21, no. 2, p. 92, pi. 20, figs. 1-3; Elias, 

 1956, Petroleum Geology of southern Okla- 

 homa: Am. Assoc. Petrol. Geol., v. 1, p. 109, 

 pi. II, figs. 9, 10. 



Neoprioniodus scitulus (Branson and Mehl), Rex- 

 road, 1957, Illinois Geol. Survey Rept. Inv. 

 199, p. 35, pi. 2, figs. 22, 26. 



Neoprioniodus striatus Rexroad, 1957, ibid., p. 35, 

 pi. 2, figs. 11, 12. 



This is an abundant and somewhat vari- 

 able species in the Glen Dean Formation. 

 The anterior margin of the fang, viewed 

 laterally, may be straight or convex in the 

 adult and is usually more convex in the 

 young. The length of the aboral projection 

 of the fang varies as does the outline of the 

 aboral margin. The outline may be slightly 

 convex posteriorly or straight, more convex 

 in the young specimens which may have 

 well developed, slightly flaring lateral lips, 

 which disappear in the adult form. The 

 base of the aboral projection is excavated in 

 the young but fills in during growth leav- 

 ing a tiny pit with a longitudinal median 

 groove extending anteriorly and posterior- 

 ly from it. With growth lateral attachment 

 scars may become prominent on the aboral 

 projection of the fang. Other variations 



