6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



The detailed spiral-sculpture drawings were made by John Parker, 

 of Washington, D, C, who prepared the studies under my supervision 

 in my laboratory. 



Family PYRAMIDELLIDAE 



Gastropods with the radula absent or obsolete; the operculum 

 ovoid paucispiral, with the apex anterior, a threadlike arcuate ridge 

 on the proximal side, the inner margin notched in harmony with the 

 plaits of the pillar when prominent; foot short, moderately pointed 

 behind, with a small operculigerous lobe above and sometimes a small 

 tentacular appendix on each side, in front feebly auriculate or un- 

 dulate ; mantle feebly canalif erous on the right upper margin ; a single 

 branchia; verge subcylindric, elongate; head with two flattened sub- 

 triangular or elongate tentacles, connate, grooved, or auriform in the 

 larger forms, the funicles with a ciliated area; eyes behind or be- 

 tween the bases of the tentacles; below the tentacles an oral orifice 

 from which extends a long retractile subcylindric proboscis, but there 

 is no muzzle like that of Scala; below the oral orifice is an organ 

 named by Loven the mentum, which is usually more or less medially 

 grooved or fissured, and hence, at its anterior end, more or less 

 bilobate, and extensile or retractile before or behind the front margin 

 of the foot. The shell is turrited, with a plicate axis ; the outer lip 

 frequently internally lirate; in the larger forms the aperture is ob- 

 scurely channeled in front; the larval shell is sinistral, the adult 

 dextral, the former frequently set at an angle to the adult axis, or 

 more or less immersed in the adult apical whorls ; it is usually helicoid 

 and smooth; the sculpture varies from nothing to ribbed, spirally 

 sulcate or reticulate ; the coloration when present usually reddish, 

 brownish, or yellow. The eggs are numerous and deposited in a len- 

 ticular mass. The distribution is worldwide, but the larger forms are 

 mostly tropical. 



The pyramidellids, numerically speaking, are the dominant family 

 of marine mollusks in modern seas. In superspecific groups they are 

 excelled only by the turrids. 



KEY TO THE SUPERSPECIFIC GROUPS OF THE FAMILY PYRAMIDELLIDAE 



REPRESENTED IN THE PLIOCENE FAUNA OF 



NORTH ST. PETERSBURG, FLA.^ 



Columellar folds 3. 



Axial ribs present. 



Spiral cords present Triptychus 



Spiral cords absent (Plmrcidella) 



Axial ribs absent Longchaeus 



