212 Trans. Acad. Sci. of St. Louis. 



older type, even DevoDian, has been recorded by Williams,* 

 but this Batesville fauna seems to have migrated eastward 

 from the southwestern region. The eastward migration from 

 the northwest of the fauna containing persistent Kinderhook 

 types, probably occurred at approximately the same time as a 

 similar migration from the southwest the evidence of which 

 is recorded in the rocks of Arkansas. 



EXPLANATION OF ILLUSTRATIONS. 



Plates XII-XX. 



(unless otherwise stated, all figures are of natural siz^.) 



Plate XII. — 1. Chonopectus fischeri (N. & P.). U. of C. Coll. No. 6655. — 

 2. Ghonetes gregarius n. sp. U. of C. Coll. No. 6654. — 3. i2Aipidome«a 

 burlingtonensis (H.) U. of C. Coll. No. 6656.-4-7. Holopea conica Win. 

 4. Type of H. conica. 6. Type of H. mira. 7. Type of H. subconica. U. of 

 M. Coll. Nos. 1459, 1460. — 8. Microdon leptogaster (Win.) Type specimen. 

 U. of M. Coll. No. 1431. — 9. Aviculopecten iowensis Miller. Type speci- 

 men. U. of M. Coll. No. 1396. 



Plate XII r.— 1-3, Syringothyris halli Win. Three views of the most per- 

 fect of the type specimens. U. of M. Coll. No. 1^%^. — ^-%. Bhynchopora 

 pustulosa (White). Three views of one of the type specimens. U. of M. 

 Coll. No. 1377. — 7-13. Camarotoechia '^ heteropsis (Win.), 9-10. Two views 

 of one of the type specimens, and 11-13^ three views of another of the types 

 of U. M. Coll. No. 1997. 7-8. Two views of the type of M. unica Win. U. of M. 

 Coll. No. 1999. — 14-16. Pugnax striaticostata (M. & W.). Three views of a 

 very perfect specimen. The radiating striae are not shown in the drawing. 

 U. of C. Coll. No. 6658.— 17. Chonopectus fischeri (N. & P.). U. of C. Coll. 

 No. 6657. 



Plate XIV.— 1-2. Spirifer marionensis Shum. Two views of a pedicle 

 valve. U. of M. Coll. — 3-4. Spirifer centronatus Win. Views of a pedicle and 

 a brachial valve. U. of C. Coll. No. 6660. — 5. Cyrtina acutirostris (Shum.) ? 

 View of a brachial valve. U. of C. Coll. No. 6663. — 6-9. Spirifer peculiaris 

 Shum. ? 6-7. Views of a brachial and a pedicle valve. 8. View of a wax 

 impression from a natural mould showing an elongate hinge -line and a 

 sharply defined cardinal area.— 9. Lateral view of an internal cast. U. of M. 

 Coll. Nos. 1362, 1363, 1413. — 10. Dielasma allei (Win.). The type speci- 

 men. U. of M. Coll. No. 2004.-11-13. Camarophorella lenticularis (W. & W.). 

 11. A pedicle valve, 12-13, brachial and lateral views of another speci- 

 men. Type specimens. U. of M. Coll. No. 1356. — 14-15. Meticularia coop ■ 

 erensis (Swall.). A pedicle and a brachial valve. U. of M. Coll. No. 

 1367. — 16-18. Orthothetes inaequalis (Hall). Views of three specimens, one 

 pedicle and two brachial valves. U. of C. Coll. No. 6662. — 19-20. Leptaena 

 rhomboidalis Wilck. U. of C. Coll. No. 6659.— 21-22. Productus parvulus 



Am. Jour. Sci. 49 : 94-101. 



