MOLLUSCOIDEA. 319 



towards the anterior carina and arranged in more or less irregular 

 transverse series, about five or six occupying the space of i mm. ; 

 posteriorly they become more scattered and may become entirely 

 wanting upon the rounded posterior surface. Zooecial apertures 

 subcircular or oval, slightly oblique, surrounded by a slightly 

 raised peristone which is a little higher behind than in front. 

 Smaller mesopores occupy the spaces between the zocecia. 



Remarks. — Besides its occurrence in the Vincentown limesand, 

 this species has also been recognized in the Eocene of Maryland. 

 A very similar, perhaps identical, form from the Upper Cre- 

 taceous (Senonien) of France has been described under the name 

 Bicrisina gaudryana Pergens.^ 



Formation and, locality. — ^Vincentown limesand, Vincentown 

 (154), Timber Creek (Gabb and Horn). 



Geographic distribution. — New Jersey, also Eocene of Mary- 

 land. 



Genus Crisina d'Orbigny. 

 Crisina striatopora Ulricli. 



Plate XXI., Figs. 15-18. 



1904. Crisina striatopora Ulrich, Md. Geol. Surv. Miocene, p. 

 406, pi. 117, figs. 1-4. 



Description. — "Zoarium erect, ramose, probably not exceeding 

 I cm. in height, dividing dichoto^mously at intervals of about 1.5 

 mm. ; branches subovate in cross-section, thickest uniformly 

 convex and traversed longitudinally by from 16 to 20 

 punctate striae on the reverse side, narrower and carrying alter- 

 nating series of zooecial apertures on the obverse side. Zooecial 

 apertures rarely three usually four in each series, in contact later- 

 ally, the inner one of each series largest, most prominent, and 

 subcircular, the outer one, smallest, drawn out distally and ap- 

 parently grading into the pores lying between the longitudinal 

 ridges of the reverse side. Series of zooecia curving first forward 

 then slightly backward, separated by a deep interspace averaging 



' Bull. Soc. Belg. de Geol., vol. 3, pi. 13, fig. 2. 



