GENER.A OF THE SUBORDER ORTHOIDEA 



147 



are diagnostic characters. From Orthotichia it differs 

 in the presence of the anterior ph'cations and in the sub- 

 parallelism of the dental plates. It differs from Entele- 

 t'tna and Parentcletes in having the fold on the dorsal 

 valve. EnteleteUa differs from this genus in the posses- 

 sion of a spondylium. 



Discussion. — Waagen**^ proposed two groups of 

 EnteUtes: ( 1 ) the "ventrisinuate" group having the 

 fold on the dorsal valve; and (2) the "dorsosinuate" 

 group which has the fold on the ventral valve. 

 King^"" has recently separated the latter group as a 

 new genus called Parenteletes. The new generic 

 group is, however, not homogeneous and should be 

 further split into two groups on the basis of internal 

 structure. The term Enteletes, then, must be re- 

 stricted to shells of the E. lamarcki and E. hemiflicatus 

 type, which have the fold and sulcus in the usual 

 position. Specimens having a small sulcus in the fold 

 and a plication in the sulcus are not excluded from 

 Enteletes; this condition does not alter the uniplicate 

 character of the anterior commissure and is not con- 

 sidered of sufficient import for the separation of a 

 new group. 



VVaagen*"^ suggested that Enteletes evolved from 

 Orthotichia by the development of plicas in the anterior 

 part of the shell, and this idea has gained quite general 

 acceptance. Enteletes is the culmination of a long 

 line of orthid evolution that began in Chazy time with 

 Pionodema. It appears in the Middle Pennsylvanian 

 and ranges through the Permian. By loss of the plicas 

 in late Permian time it is thought to have returned to 

 the ancestral Orthotichia-like condition, this atavistic 

 phase of Enteletes being termed Enteletoides by 

 Stuckenberg. 



It is thought by the writers that Orthotichia, which 

 ranges from the Pennsylvanian to the Permian, is 

 probably a terminal stock of the Schizophoriidas and 

 may not have given rise to Enteletes. We suggest the 

 separate development of Enteletes out of Schizophoria 

 in the Pennsylvanian at about the same time as the 

 appearance of Orthotichia. 



Gorsky'"^ has claimed the development of Enteletes 

 from Orthotichia by way of simply plicated stocks like 

 Aulacofhoria. We hold, rather, that Aulacophoria is 

 a side line out of Schizophoria, and one that probably 

 did not survive beyond the middle Pennsylvanian. 



Genus PARENTELETES King 1931 



PI. 24, figs. 11, 13, 14, 16, 18, 21, 26 



King, Bull. 3042, Univ. Texas, 1930 (1931), p. 48, pi. 1, 

 figs. 16-20; pi. 2, figs. 1-3. 



"• Mem. Geol. Surv. India, Pal. indica, ser. XIII, vol. 1, 

 pt. IV', fasc. 3, pp. 5 5 3-563. 



'" Bull. 3042, Univ. Texas, 1930 (1931), p. 48. 

 "' Op. cit., p. 564. 



122 



Op. cit., 1927. 



Genoholotype. — P. cooperi King 1931. 



Description. Exterior. — Externally like Ente- 

 letes, but somewhat more transverse, dorsosinuate; 

 lateral profile unequally biconvex, the dorsal valve the 

 larger; anterior commissure sulcate ; ventral interarea 

 the longer, apsacline, beak strongly incurved, umbo 

 swollen, delthyrium large; dorsal interarea short, 

 curved, apsacline, beak strongly incurved, umbo tumid, 

 notothyrium wide. Surface multicostellatc and plicate, 

 rugose, with hollow costella-, the plica broad and 

 angular. Shell fibrous, punctate, the punctx arranged 

 in narrow radial rows. 



Ventral interior. — Delthyrial cavity deep, teeth 

 elongate, sockets pointed; dental plates strong, sub- 

 parallel posteriorly but diverging strongly anteriorly; 

 area between them divided by a median septum which 

 originates very close to the apex, rounded on its dorsal 

 extremity, rising as it progresses forward to reach its 

 maximum height at the point where the anterior ends 

 of the dental plates die out. Here it is abruptly trun- 

 cated and its extremity forms the crest of a V-shaped 

 camera or cella, formed at the point where the internal 

 sulcus corresponding to the fold has its origin. Muscu- 

 lature as in Enteletes. A small plate for pedicle attach- 

 ment is in the apex. 



Dorsal interior. — Cardinalia and musculature like 

 those of Enteletes. 



Geologic range. — Upper Pennsylvanian and 

 Lower Permian of Europe and America. 



American Species 

 Parenteletes cooperi King 1931 



Foreign Species 



Enteletes dieneri Schellwien 1900 



E. suessi Schellwien 1892 



E. suessi acuticosta Schellwien 1892 



Distinguishing characters. — Parenteletes dif- 

 fers from Enteletes in having the fold on the ventral 

 valve, and in the possession of a V-shaped camera or 

 cella under the anterior portion of the median septum. 

 This internal character also serves to differentiate the 

 genus from Enteletina, which closely resembles it 

 externally. 



King has shown that Parenteletes in America ap- 

 pears in geological time before Enteletes, and this 

 appears to indicate that the genus under discussion 

 evolved separately from Orthotichia or Schizophoria 

 and is not a modification of Enteletes. Girty'"^ and 

 Waagen'"'' have suggested that Parenteletes (the dor- 

 sosinuate group) developed out of an Enteletes having 



'" U. S. Gcol. Surv., Prof. Paper 5 8, 1908, p. 290. 

 '" Mem. Geol. Surv. India, Pal. Indica, ser. XVIII, 

 vol. 1, 1887, p. 562. 



