1916] Nomland: Fauna from the Lower Pliocene 207 



NATICA (NEVERITA) ORBICULARIS, n. sp. 

 Plate 10, figures 4a, 4b 



Shell globular, heavy, about five or six whorls, spire slightly ele- 

 vated. Sculptured by unequal oblique incremental lines. Body whorls 

 large, with marked convexity at shoulder, giving sides and top a flat- 

 tened appearance. Aperture ovate, with slightly thickened outer lip. 

 Umbilicus partly covered by callus extending from lower portion of 

 inner lip to upper portion of outer lip, with a sharp angle near the 

 middle, and is marked by a deep groove about one-third of distance 

 from posterior end. Height, 38 mm. ; maximum diameter, 44 mm. 



This species differs from Ncverita recluziana Petit by its more 

 flattened sides, dome-shaped spire, less callused umbilical area, and 

 greater convexity at shoulder of whorls. 



Occurrence. — Found at numerous localities in the Jacalitos and 

 Btchegoin. Type from University of California locality 2679. 



TIVELA TRIGONALIS, n. sp. 

 Plate 9, figures 2a, 2b, 2c 

 Shell thick, trigonal, inequilateral, equivalve. Umbones small, about 

 two-thirds of distance from anterior end. Base gently arcuate. An- 

 terior dorsal edge nearly straight, depressed. Anterior extremity 

 evenly rounded. Posterior dorsal margin straight, much thickened. 

 Posterior end bluntly rounded to subangulate. Three thick cardinal 

 teeth in each valve, the middle left bifid, anterior lateral of left valve 

 heavy. Nymph plates very prominent grooved. Height, 41 mm. ; 

 width, 55 mm. 



Although somewhat similar to the Eecent Tivela stultorum Mawe, 

 T. trigonalis, n. sp., may easily be distinguished from that form by 

 being more inequilateral, thick, depressed posterior dorsal margin, and 

 greater prominence of nymph plates. 



Occurrence. — Middle Jacalitos to lower Etchegoin, University of 

 California localities 2684, 2104. 



TROPHON MAGISTER, n. sp. 

 Plate 11, figures 4a, 46, 4c 

 Shell very large, robust, thick, height of spire variable. Whorls 

 five or more, slightly convex, with appressed suture. Body whorl 

 sharply angulated at base and shoulder, giving the top a tabulate 



