;8 4 



DIVISIONS OF THE GASTROPODA. 



Fig. 684. — A, Eulima vagans, Jurassic (after 

 Morris and Lycett) ; b, Pyramidella Iceviuscula, 

 Pliocene (after Searles Wood); c, Chemnitzia 

 intemodula, Eocene (after Searles Wood). 



In Pyramidella (fig. 684, b) the shell is slender and turreted, 

 and the columellar lip is plaited. The genus is represented by a num- 

 ber of Recent and Tertiary species, while still older forms occur in 

 the Cretaceous rocks. Odostomia, with a similar geological range, 



includes minute turreted shells 

 very similar in most respects 

 to Pyramidella, but having a 

 single tooth-like columellar fold. 

 Turbonilla, with the same range 

 in time, nearly resembles the 

 preceding, but the columellar 

 lip is simple, or has a feeble 

 oblique fold. Chemnitzia (fig. 

 684, c) includes a number of 

 slender, turreted, many-whorled 

 shells, with plaited whorls and 

 a simple aperture, the columellar lip having neither teeth nor folds. 

 Numerous fossil forms are known in the Triassic, Jurassic, and 

 Cretaceous deposits, in marine sediments only ; and there are also 

 Tertiary species. It is doubtful if the distinction between Chem- 

 nitzia and Turbonilla can be maintained. Eulima (fig. 684, a) 

 includes small, polished, elongated shells, with level whorls and a 

 reflected inner lip. The genus ranges from 

 the Trias to the present day, a large number 

 of species occurring in the Tertiary deposits. 

 JVzso, with the same geological range, has the 

 shell umbilicated, but otherwise resembles Eu- 

 lima. 



Family 27. Pseudomelaniid^e. — This family 

 has been founded for the reception of certain 

 extinct marine Gastropods, of which Loxonema 

 and Macrocheilus are the two most important 

 types. In this family the shell is many-whorled 

 and turreted, with an oval aperture, which is 

 typically entire, but is occasionally notched in 

 front. The columella is simple, or may be 

 slightly folded anteriorly. The forms included 

 in this family have a general resemblance to 

 Melania, but they are found in deposits of 

 marine origin, whereas the Melanice are inhabi- 

 tants of fresh water. 

 The shell in Loxonema (fig. 685) is long and turreted, with con- 

 vex whorls, which have no spiral band ; and the surface is covered 

 with longitudinal, often more or less arched strise or ribs, while 

 the outer lip is more or less sinuated. The genus ranges from the 



Fig. 685. — Loxone 

 via rugifera, Carbon 

 iferous Limestone 



(After Phillips.) 



