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821 



TERTIARY FAUNA OF FLORIDA 



not complete, but the general form seems to have been oval or rounded, with 

 no signs of segmentation, furrows, or additional accessory plates, which, 

 indeed, would be quite needless. Lon. 12, lat. 8.5, diam. 7 mm. 



This singular shell recalls Martcsia obtccta Sby. in its enormous proto- 

 plax. Say's description of his Pholas ovalis is insufficient to identify his shell 

 without a figure or typical specimen. I have wondered if it could be possible 

 that the " tube" in which his shell is said to have been enclosed could by any 

 chance have been a poorly observed or imperfect protoplax of this kind. It 

 is, of course, impossible to decide without further information, but Say's 

 descriptions are usually so clear and good, and his observing powers were 

 so keen, that I can hardly suppose him to have used the word " tube" for 

 an appendage of this kind without some explanation or modification. 



This species appears to be related to the Pholas saitata Deshayes (An. s. 

 Vert. Bassin de Paris, i., p. 137, pi. vi., figs. 5, 6, i860), for which and similar 

 species he proposed the sectional name Scutigera. This name being pre- 

 occupied since 1802 for a genus of Myriapods , Fischer proposed to replace it 

 by Aspidopliolas (Man., p. 11 37, 1887). The French species secretes a cal- 

 careous tube or siphonoplax, though none such was found with the present 

 shell. This may be due to immaturity or other accidental circumstance, and 

 the adults may possess such a tube, which may be what Say referred to. 



Genus XYLOPHAGA Tuiton. 

 Xylophaga Turton, Dithyra Brit., p. 527, 1822. Type .V. dorsalis Turton. (Not Xyh- 

 pliagiis Meuschen, 178S.) 



Shell like that of Teredo, but with a double protoplax and the internal 

 apophyses obsolete; soft parts contained within the shell, without callum, 

 siphonoplax, or calcareous tube. There is sometimes a calcareous lining to the 

 excavation made b)- the animal, according to Fischer, but none of the borings 

 I have seen from this animal exhibit it. 



If, according to the very obnoxious practice of some authors, the name 

 Xylophaga inust be rejected on account of the existence of the ancient syno- 

 nyme Xylophagiis, the name inight be changed to Xylotouiea, but our own 

 opinion is strongly adverse to such changes. 



Xylophaga mississippiensis Aldrich, 1886, has been described from the 

 Eocene of Newton, Mississippi, but from the figure it is somewhat doubtful if 

 the species is really a member of this genus. Pholas rhoinboidca H. C. Lea, 

 1845, from the Miocene of Petersburg, Virginia, is probably a Xylophaga. 



