MARYLAND GEOLOGICAL SURVEY 99 



which it might be confounded. Compared with European forms, 

 Cytliere striatopunctata (Eoemer), C. scrohiculata (Miinster), C. nystiana 

 and C. angulatopora Bosquet as figured by Bosquet/ are more or less 

 closely allied but it is so easily distinguished from each of those men- 

 tioned by differences in outline and surface markings that we have no 

 doubt of its distinctness. 



The specific name is given in honor of Professor William Bullock 

 Clark, the State Geologist of Marjdand. 



Occurrence. — Calvert Formation. Plum Point.' Chesapeake 

 Group. Yorktown, Pa. 



Collections. — U. S. National Museum, Maryland Geological Survey, 



Cythere clarkana var. minuscula n. var. 

 Plate XXXV, Figs. 11-14. 



Description. — The form for which we propose the above subordinate 

 name is not uncommon in association with C. clarkana, yet, despite its 

 very similar aspect, we have not observed any satisfactory connecting 

 links proving it to be, as we believed at first, merely the young of the 

 larger form. For the present therefore we assume that it represents 

 a variety sufficiently distinct to deserve a name. So far as known it 

 is distinguished by its much smaller size and relatively wider anterior 

 end. The latter difference is noticeable in particular when right valves 

 are compared. 



Occurrence. — Calvert Formation. Plum Point. Chesapeake Group. 

 Yorktown, Va. 



Collections. — U. S. National Museum, Maryland Geological Survey. 



Cythere planibasalis n. sp. 



Plate XXXVIII, Figs. 1-3. 



Description. — Valves ovate subtetragonal, dorsal margin rather short, 

 straight, ventral margin gently convex; ends unequal, the anterior edge 



1 Desc. des Entomostraces Fossiles des Terrains Tertiares de la France et de la 

 Belgique. Mem. Couron. Acad. Belg., Tome xxiv, 1851. 



•i The OsTRACODA described from this locality were picked by the writers from a 

 small part (about a half pint) of extensive washings secured by Mr. Frank Burns for 

 the United States National Museum. The figured specimens will be preserved in the 

 National Museum, while a duplicate set, as nearly complete as possible, has been 

 selected for the collection of the Maryland Geological Survey. 



