MUSEUM OF COMPARATIVE ZOOLOGY. 311 



The peculiarity of the filling up of the tips of the beaks does not consist in 

 there being mere pedestals or sockets for the feet of the ossiculum. The 

 whole cavity seems evenly filled, and the ossicle stands, as it were, on a sort 

 of floor ; this is quite visible from without, through the translucent shell. It 

 is a common thing to find the early whorls of Gastropods filled solid with 

 shelly matter, but such cases are rare among the Pelecypods, if we leave out 

 of account the usual thickening due to growth. 



Family PANDORID^. 



Genus PANDORA Hwass. 



Subgenus CLIDIOPHORA Carpenteb. 



Of the PandoridoR the southern coasts and the Antilles have several species : 

 Clidiophora trilineata Say ; another form, of which one valve was described but 

 not named by Miss Bush ; Pandora (Kennerlia) glacialis Leach, which passes 

 Hatteras, its southern limit not yet known; P. carolinensis Bush, described 

 from near Hatteras, probably entering the Gulf of Mexico, and P. Bushiana, 

 received from West Florida. This group, being chiefly composed of shallow- 

 water species, is represented in the Blake dredgings only by worn left valves 

 of one species. 



I may add, that in this genus, as in others, I regard anterior and posterior, 

 right and left, from the anatomical standpoint. A singular discrepancy exists 

 among authors in treating of this genus, as we find the rostrated or siphonal 

 end of the shell frequently treated as anterior. As a matter of fact, it is pos- 

 terior, as in other Pelecypods. 



Pandora (Clidiophora) carolinensis Bush. 



Pandora carolinensis Bush, Trans. Conn. Acad., VI. p. 474, 1885. 

 Pandora oblongaf Sowerby, Dall, Bull. M. C. Z., IX. p. 109, 1881. 



Plate VIII. Figrs. 8, 8 a. 



Habitat. Charlotte Harbor, Florida, 13 fms.; Yucatan Strait, 640 fms., 

 detached valves only. 



I presume that the valves above mentioned should rightly be referred to 

 Miss Bush's species. Whether both are referable to P. oblonga is a question 

 on which opinions may differ, as the type of oblonga is said to be lost. 



They are not referable to P. trilineata Say (not Gould, etc.), which is a 

 much elongated, slender, narrowly rostrated species with the beaks more an- 

 terior even than P. hrevifrons Sby.; the base roundly arcuated, the posterior 

 cardinal margin concave, the anterior rounded from the beaks to the base, the 



