156 University of California Publications in Geology [Vol. ll 



Solen (Plectosolen) curtus Conrad, Dall, U. S. Geol. Surv., Prof, paper 



no. 59, p. 129, 1909. 

 ? Solen curtus Conrad, Arnold and Hannibal, Proc. Am. Philos. Soc, vol. 



52, no. 212, pp. 583, 584. 

 Solen curtus Conrad, Clark, Univ. Calif. Publ., Bull. Dept. Geol., vol. 9, 



no. 2, pp. 15 and 18, 1915. 

 Occurrence. — University of California localities 11, 1131, 1312, 2753, etc. 



Solen curtus is a much smaller form than the ordinary Solen; 

 the anterior end is obliquely rounded and the posterior dorsal margin 

 is slightly concave similar to S. sicareus Gould, 125 a common Recent 

 species on the West Coast. S. curtus is reported by Arnold and Han- 

 nibal (Proc. Amer. Philos. Soc, vol. 52, no. 212, pp. 583-584) as 

 having a range from Oligocene to Recent ; the writer doubts very 

 much whether it occurs above the Lower Miocene. It seems probable 

 that the writers referred to have, at least in part, confused S. curtus 

 with another species. S. curtus is found in the Lower Miocene 

 beds near Bakersfield, California; these beds belong to the Turritella 

 ocoyana zone. 



SOLEN GEAVIDUS, n. sp. 



Plate 10, figure 7 



Type specimen 11133, Coll. Invert. Palae. Univ. Calif., loc. 1131 



Shell large and rather heavy. Posterior dorsal and ventral edges straight 

 and parallel with each other. Posterior end regularly rounded ; anterior end 

 regularly and gently rounded, with highest point of convexity a little below 

 the middle. Shell subangulate at junction of anterior dorsal and ventral edges. 

 In the right valve there is a heavy, bifid, deltoid cardinal; in the left valve 

 the cardinal is heavy and elongate, with the highest point anterior, sloping down 

 rapidly posteriorly. On surface near anterior end there is a narrow, shallow 

 groove or sinus which slants obliquely from beaks to anterior end of ventral edge; 

 the margin between this sinus and the anterior dorsal edge is somewhat variable 

 in 'width on different specimens ; the sinus is also variable in depth. Anterior 

 end of shell thickened internally just back of anterior dorsal edge and in front 

 of sinus. 



Dimensions. — Length, 93 mm.; height, 15 mm.; diameter of both valves, about 

 10 mm. 



Occurrence. — University of California localities 1131, 1173, 1213, etc. 



There has been a tendency for different workers on the palaeon- 

 tology of the West Coast to disregard the species of the genus Solen. 

 The average published faunal list of Miocene and Pliocene species 

 contains the species Solen sicareus Gould. The Solens, like the 

 Xaticas, require well-preserved specimens in order to obtain the 



125 For original description of Solen sicareus see Proc. Bost. Soc. Nat. Hist., 

 vol. 3, p. 214, 1850. For good redescription see Arnold, Mem. Calif. Acad. Sci., 

 vol. 3, p. 172, 1903. 



