218 
SELA.CHII. 
of Towa and Illinois ; D. ? exornatus (tom. cit. p. 168, pi. xi. fig. 14), 
from the Warsaw Limestone of Illinois; D. ? inflexus (tom. cit. 
p. 167, pi. xi. fig. 13), from the Iveokuk Limestone of Illinois ; D.? 
Jceohuk (tom. cit. p. 169, pi. xi. fig. 16), from the Keokuk Limestone 
of Illinois ; and D. sancti-ludovici (tom. cit. p. 161, pi. xi. figs. 2-6), 
from the St. Louis Limestone of Iowa, Illinois, and Missouri. Del- 
toclus cingustus, Newberry and Worthen, is also placed here. 
The genus Chalcodus, Zittel (Handb. Palgeont. vol. iii. pt. i. 1887, 
p. 72), from the German Kupferschiefer, though originally referred 
to the Cochliodontidce, does not appear to belong to this family ; 
and a brachiopod shell 1 from the Upper Carboniferous of Lo-Ping, 
China, has also been placed here, under the name of Leptodus 
richthofeni , E. Kayser (Eichthofen’s Beitr. Palaont. China, 1883, 
p. 161, pi. xxi. figs. 9-11). 
Undetermined Anterior Teeth. 
The anterior teeth of the Cochliodontidge have been described 
under the provisional generic names of Helodus, Agassiz (Poiss. 
Loss. vol. iii. 1838, p. 104) ; Chomatodus , Agassiz (tom. cit. 
p. 107); Lophodus, Bomanowsky (Bull. Soc. Imp. -Nat. Moscou, 
vol. xxxvii. 1864, pt. ii. p. 160); and perhaps Venustodus , St. John 
and Worthen (Pal. Illinois, vol. vi. 1875, p. 344). Those named 
Helodus planus by Agassiz are known to be certainly referable to 
Psephodus mcignus ; and most of the teeth from the Bristol Bone- 
bed, named Helodus Icevissimus, doubtless pertain to Psephodus 
Icevissimus. The other teeth, however, except H. simplex , are pro¬ 
bably common to one or more genera or species, and it is thus con¬ 
venient, upon present evidence, to retain the provisional determina¬ 
tions, as follow. Unless otherwise stated, the specimens were all 
obtained from undetermined horizons in the Carboniferous Lime¬ 
stone. 
I. Large elongated depressed teeth, generally with a longitudinal 
elevation near one of the long margins, often rising into a 
median prominence. Such have been described under the 
names of Chomatodus ductus, Agassiz 2 , Helodus turgiclus , 
1 Lyttonia, W. Waagen, Palasont. Indica [13] pt. iv. (1882), p. 395. 
2 Poiss. Foss. vol. iii. (1838), p. 107, pi. xv. figs. 13-21 (in part). Also 
J. E. Portlock, Eep. Geol. Londonderry (1843), p. 467, pi xiv.«. fig. 9 ; L. G. de 
Koninck, Faune Calc. Carbf. Belg. pt. i. (1878), p. 46, pi. iv. fig. 3, pi. xi. figs. 1-5. 
Helodus cinctus, F. McCoy, Brit. Pakeoz. Foss. (1855), p. 617. 
