M\|;^|.\\|t (;i:()i.()(;i('.\i, srit\'i:Y 121 



angusticoshilii l)(is(|., ('. iiKicrn/iurd \\i)>i\. iiinl ('. i'<linir(l.<\ ( IJdchht), all 

 Eocene species except the last, wliicli is a widely (listriimtcil Miocene 

 J'ossil. Despite the oflcii striking- similarities preseiiled. iml one of the 

 i'lnidpean species mentioned a«ri"ees closely enon<:h in all rrspecls to 

 jnsiify a relerence of the Maryland form to il. 



Cijlhcrcis hiisslcri. which I name in honor of my ahle and indefati<?al)le 

 assistant, Mr. \l. S. r>assler, ^eem^ to he a common fo-.-ii at I'pper Marl- 

 horo. Considerini;- that the speciniens studied pre>ent considerable 

 v:ii'iali(Mi in snrl'ace sculpt inc. it is possible that they i'e]iresent more 

 than a single speeitic type. I have also a specimen from the Cretaceous 

 at Vineentown. X. J., which can scarcely be disl in.iiinshed from the 

 Upper j\Iarlhoi'o .specimen lliiin'ed. 



(hTiirrciicc. — Aquia I-'ohmatiox. T"])])er Mar]l»oro. 



Collcclioii. — ^faT'yland ( ieolo,i;ical Survey. 



Genus CYTHERIDEA Bosquet. 



Cytiieridka peharcuata n. pp. 

 Plate XVI, Fig. 23, 23. 

 Z)escr//;//o/(.— Carapace 1.1 mm. long. O.fi mm. higli. sti'onglv and, ex- 

 cepting the acuminate posterior extremity, rather uniformly convex, 

 obliquely acute-ovate in outline; ventral edge straight to the acute pos- 

 terior extremity, the sharpness of which is emphasized by a small spine; 

 anterior outline wide and regularly rounded, and armed with five or 

 six spines; dorsal side strongly arcuate, the curve straightening some- 

 "what as it nears the posterior end. Central portion of surface, over a 

 space corresponding in shape with the outline of the valves, marked 

 with eleven or twelve approximately vertical furrows, each including 

 a row of small punctures. Beyond this space the surface is smooth, ex- 

 cepting toward the posterior end where an obscm-ely wrinkled appearance 

 may be observed. Ventral edge of right valve with a narrow bevel in-, 

 ward. Hinge as required by the genus, consisting of a series of small 

 denticles at each end of the hinge in right valve and corresponding 

 sockets in the left valve. Edge view broadly lanceolate, thickest near the 

 middle length and slightly more attenuate behind than in front; end 

 view subcircular. 



