140 PROCEEDINGS OF THE ACADEMY OF [1890. 



Tryblionella Hantzschiana, Grim. 



Tryblionella scutellum, W. Sm. 



Many of the forms are found everywhere from top to base of this 

 section. Among these Meloslra sulcata is one of the most frequent. 

 Others are found predominating only at certain horizons ; among these 

 may be noticed a beautiful iridescent, many-rayed disc form, Act'in- 

 ocyclus Ehrenbergii which is chai'acteristically abundant at 625 feet ; 

 it occurs sparingly at 525 feet but is scarcely if at all seen at 400 feet. 



At about 525 feet the genus Rhaphoneis, an elongated form, occurs 

 more frequently than elsewhere and in many varieties. Associated 

 ■with it at this same depth are a number of rare forms heretofore 

 found only in this country in an Artesian well at Cambridge, Md., 

 at a depth of 275 feet, and again in a well at Fortress Monroe at a 

 depth of 558 feet. The general resemblance seen in strewn mounts 

 from Cambridge and Atlantic City is so great as to suggest an exact 

 identity of strata. More light, however, will be needed to definitely 

 settle this point. 



Respecting Rhapho7ieis, the variety of forms grading almost 

 insensibly from one to the other is so great that it is possible to so 

 arrange a dozen or more side by side in a line that differences are 

 not readily appreciable except by skipi:)ing over ijitermediate forms 

 and comparing those some distance apart. In fact, T. Christian has 

 shown me a slide containing 16 such forms from the Cambridge well, 

 and C. Henry Kain has remarked respecting these same forms at 

 Atlantic City, that they " present such variations of structure as to 

 suggest the advisability of decreasing the number of species usually 

 considered as belonging to this genus." 



There is a curious anomaly in connection with a newly described 

 elongated species, Biddulphia Brittoniana, found at 525 feet. In 

 this the two frustules composing one individual and usually present- 

 ing their convex sides outward, have never been observed in 

 that manner, but instead, two frustules separated from different 

 individuals are found with their convex sides inward and fastened 

 together by the interlocking of curiously hooked seta; at both ends 

 of each frustule. 



At 425 feet five foraminiferal forms are associated with the 

 diatoms. After chemical treatment of earth from this depth for the 

 cleaning and sej^aration of the diatoms one species of foraminifera, a 

 Textularia remained intact in the form of a siliceous infernal cast — 

 the shell having been destroyed bv the acids used. 



