MOLLUSCA. 491 



the Navesink marl, and Morton's original specimen is one of 

 these shells. 



FormOftion and locality. — Navesink marl, near Crawfords Cor- 

 ners (126''), Crosswicks Creek (147*, 149), near Holmdel 

 (1285), near Jacobstown (150), MuUica Hill (169), Holmdel 

 and Freehold (Whitfield). 



Geographic distribution. — ^New Jersey- 

 Lima whitfieldi n. sp. 

 Plate LIV., Pig. 8. 



1886. Radula pelagica Whitf., Pal. N. J., vol. i (Monog. U. S. 

 G. S., vol. 9), p. 61, pi. 9, fig. 4 (not figs. 3 and 5). 



Description. — The dimensions of the type specimen are: 

 extreme length, 25 mm.; greatest width, 21.5 mm.; length of 

 hinge-line, 8 mm.; convexity of one valve, 7 mm. In general 

 form and proportions this shell is essentially identical with R. 

 pelagica, but it has not been observed to attain so large a size as 

 that species, and differs fundamentally in the character of the 

 surface markings. In this species the plications and interspaces 

 are always rounded and lack entirely the secondary riblets which 

 are present in the bottom of the interspaces in R. pelagica. In 

 addition to the ribs the shell is entirely covered with fine con- 

 centric markings. 



Remarks. — The type of this species is one of the specimens 

 which Whitfield illustrates as R. pelagica. The specimen has the 

 shell well preserved, showing all the surface features, as well as 

 the hinge; it is preserved in a rather coarse sand cemented with 

 calcium' carbonate, the so-called "limestone nodules" of Whitfield, 

 said to come from the base of the "lower marl." The horizon of 

 these calcareo-arenaceous masses as observed in recent field work, 

 is near the very base of the Navesink, or in the uppermost beds 

 of the Wenonah. A few other specimens from the Marshalltown 

 clay-marl are referred to this species, although they differ some- ' 

 what from the type in having narrower interspaces between the 

 ribs and in having stronger concentric markings. 



Formation and locality. — Marshalltown clay-marl, near 

 Swedesboro (177); Navesink marl, near Holmdel (Whitfield). 



