NOTES ON CARBONIFEROUS COCHLIODONTS 27 



of the closely allied genus, Cockliodus, three teeth were present on 

 each ramus, and it has already been shown in this paper that the 

 same is true of Psephodus. Davis figures one specimen of Deltodus 

 dentition with two teeth in position on one ramus. 1 In discussing 

 this specimen he says: 2 



Connected with u he posterior tooth a second one, hitherto regarded as a sepa- 

 rate species under the name Poecilodus parallelus, has been found, which leaves 

 no room to doubt that it is in its natural position, and from the character of its 

 inside margin leads to the natural inference that a third tooth occupied the front 

 or median portion of the lower jaw. 



In all median teeth of Deltodus that are known the anterior edge is 

 truncate or grooved, as if for articulation with other teeth. 

 Eastman says 3 that analogy of Deltodus with Cockliodus 



leads us to expect, in advance of the anterior dental plate, a series of helodus-like 

 teeth above and below, and in front of this, at the symphysis of at least one jaw, 

 a series of bilaterally symmetrical teeth, arched in a single plain, and corresponding 

 to the form described by Newberry as Helodus coxanus. 



No specimen of Deltodus furnishing any evidence in proof of this is 

 known, and if, as it seems most probable, Cockliodus had no helodus- 

 like teeth, there is nothing left to support such a hypothesis as to 

 the dentition of Deltodus. 



Sandalodus occidentalis Leidy 



(Plate I, Figs. 8 and 9) 



Cochliodus occidentalis Leidy, 1857 {Transactions of the American Philosophical 



Society (2), Vol. XI, p. 88, Plate V, Figs. 3-16). 

 Deltodus stellatus Newberry and Worthen, 1866 {Paleontology of Illinois. Vol. II, 



p. 97, Plate IX, Fig. 2 [not Fig. 3]). 

 Deltodus complanatus Newberry and Worthen, 1866 {ibid., p. 98, Plate IX, Fig. 4). 

 Deltodus complanatus Newberry and Worthen, 1870 {ibid., Vol. IV, Plate III, 



Figs. 5, 8, and 12). 

 Deltodus occidentalis St. John and Worthen, 1883 {ibid., Vol. VII, p. 150, Plate 



IX, Fig. 9 [not Fig. iol). 

 Deltodus intermedins St. John and Worthen, 1883 {ibid., p. 153, Plate IX, Figs. 



14 and 15). 

 Sandalodus complanatus St. John and Worthen, 1883 {ibid., Vol. VII, p. 184, 



Plate XII, Figs. 1-4). 



1 Op. cit., Series II, Plate 52, Fig. 9. 2 Ibid., p. 430. 



3 Bulletin of the Museum of Comparative Zoology at Harvard College, Vol. XXXIX, 

 p. 200. 



