A BRACKISH WATER PLIOCENE FAUNA— DALL. 229 



ably longer than the anterior, while these proportions are reversed 

 in the recent shell. The fossil is also less solid than recent shells of 

 the same size. 



Although the fossil is only represented by two broken right valves 

 the difference is so remarkable that I have no hesitation in regarding 

 it as a distinct species. 



The fossils come from station 6040, near Alexandria, Louisiana. 

 Type, U. S. Nat. Mus., No. 166286. 



MYTILOPSIS, sp. indet. 



Very young specimens of a species of Mytilopsis allied to if. leu- 

 copheatus of Conrad were found in the marl from station 6040. They 

 were too immature to be specifically identified. It is possible that 

 this is the shell referred to Modiolaria by Mr. Aldrich, or that his 

 shell may be Modiolaria lateralis Say, which is known from the 

 Phocene of Florida. 



UNIO (LAMPSILIS?) SANDRroS, new species. 

 Plate 20, figs. 4, 5. 



Shell small, soHd, bluntly rounded and inflated in front and rapidly 

 attenuated and almost pointed behind; anterior end shorter, pos- 

 terior longer, the beaks nearly at the anterior fourth of the shell; 

 beaks with one or two obsolete concentric undulations, or quite 

 smooth, small, distmctly prosocoelous; remamder of the surface 

 smooth except for famt incremental lines and a shallow sulcus close 

 to the posterior dorsal margin m each valve with an obsolete ridge 

 on each side of it; m front of and under the beaks is a wide obscurely 

 lozenge-shaped excavation, probably occupied m life by an extension 

 of the Hgament and with a sharp-edged border; ligamentary attach- 

 ment behmd the beaks linear; interior with the anterior muscular 

 scar deeply impressed, the posterior scar faint; dentition m the left 

 valve a transversely corrugated lamina, narrow and elongated, not 

 divided into teeth, under which is a cavity for the tooth of the oppo- 

 site valve; lateral tooth long, smgle, with a deep narrow sulcus above 

 it; right valve with a strong obscurely triangular corrugated tooth, 

 the distal end sharply bifid. Length of shell, 24; height, 12.5; 

 diameter about 12 mm., measured on incremental Imes of broken 

 valve, the total length of which is over 30 mm. 



Section 28, township 3, range 2, 6 to 8 miles west of south of 

 Alexandria, Louisiana, at station 6040. Type, U. S. Nat. Mus., No. 

 166288. 



There seems to be no recent species of close relationship to this. 

 From the look of the fossil the color of the nacre was probably purple. 



The locality is the "Frank Muse place," from about 48 feet below 

 the surface in a well. Specimens from station 3614, in Texas, are too 

 poor to be identified but have some resemblance to this species. 



