NO. 2023. A BRACKISH WATER PLIOCENE FAUNA— DALL. 237 



Station 6040, near Alexandria, Louisiana. Type, U. S. Nat., Mus., 

 No. 166315. 



PLANORBIS ANTIQUITUS Aldrich. 

 Planorbis antiquitus Aldrich, Nautilus, vol. 24, pt. 12, p. 140, pi. 10, figs. 16, 

 16a, 166, 1911. 



Station 6132, Aldrich and Matson. 



EXPLANATION OF PLATES. 

 Plate 20. 



Fig. 1. Mulinia sapotilla Dall, Ion. 15 mm., p. 228. 



2. Pleurobema alixus Dall, Ion. 16 mm., p. 230. 



3. Syrnola thelma Dall, alt. 2 mm., p. 234. 



4. Lampsilis sandrius Dall, from above, Ion. 32 mm., p. 229. 



5. The same, profile view of a young ehell, 20 mm. long, p. 229. 



6. Unto musius Dall, part of right valve showing sculpture of beak, Ion. 11 mm., 



p. 230. 



7. Rangia {cuneata var. ?) solida Dall, interior of right valve, Ion. 20 mm., p. 228. 



8. Heterodonax alexandra Dall, part of right valve, Ion. 8 mm., p. 228. 



Plate 21. 



Fig. 1. Potamides matsoni Dall, young shell, alt. 12 mm., p. 231. 



2. The same, side view of lip of adult shell. 



3. Planorbis ophis Dall, view of base, lat. 4 mm., p. 236 



4. The same, in profile. 



5. Pachycheilus anagrammatus Dall, a profile view of outer lip, p. 232. 



6. Pachycheilus suavis Dall, profile of the outer lip, p. 232. 



7. Potamides matsoni Dall, adult shell, alt. 28 mm., p. 231. 



8. Pachycheilus anagrammatus Dall, adult, alt. 24 mm. The upper whorls are 



less smooth than usual; p. 232. 



9. Pachycheilus suavis Dall, adult, alt. 20 mm., p. 232. 



Plate 22. 



Fig. 1. Paludestrina dngulata Dall, alt. 4.6 mm., p. 235. 



2. Paludestrina milium Dall, alt. 2 mm., p. 235. 



3. Pyrgulopsis satilla Dall, alt. 1.2 mm., p. 236. 



4. Paludestrina curva Dall, alt. 3.5 mm., p. 235. 



5. Cerithiopsis? burkevillensis Dall, alt. 10 mm., p. 231. 



6. TurrHella satilla Dall, alt. 4.5 mm., p. 233. 



7. Paludestrina aldrichi Dall, alt. 4.5 mm., p. 234. 



8. Isapis obsoleta Dall, alt. 3.5 mm., p. 233. 



9. Paludestrina turricula Dall, alt. 4 mm., p. 235. 



