1893.] NATURAL SCIENCES OF PHILADELPHIA. 223 



either from imperfect or from young specimens. This double nam- 

 ing of what is really one species has been noted by other writers. 



Respecting Dentalium subarcuatum above listed numerous casts 

 occur that have generally been referred to that species. Most such 

 casts were obtained in nearly straight short fragments. Examples, 

 however, were noted in the specimens under study that were from 

 four to five inches long, more or less bent and irregular in some 

 parts of their length, while quite straight in other parts. This 

 irregularity suggests that instead of belonging to the genus 

 Dentalium they may very probably represent casts made by the 

 filling in of the borings of some worm. This idea was suggested 

 by Professor A. Heilprin. These remarks do not, however, refer to 

 the external impressions listed as Dentalium which undoubtedly 

 belong to that genus. 



Most of the fossils occur in a bed of black sand about three feet 

 thick, interbedded between two clay beds, the lower one a thick bed of 

 black clay somewhat micaceous, and the upper one composed of two 

 divisions, as follows: that next the black sand, a ferruginous clay 

 with ironstone crusts, and the one above this, a soft, yellow clay. 

 Over these are the superficial or yellow gravels. A few fossils how- 

 ever are found both above and below the black sand but not in the 

 gravels. 



The yellow and the black clays are used for making bricks. The 

 black clay has been dug into or otherwise tested at the pits to 

 the depth of about 25 feet without getting through it. Its entire 

 thickness has, however, been ascertained to be 44 feet from a well- 

 boring recently made at Maple Shade, one mile west. 



The relative position of the fossiliferous horizon is shown in the 

 following section, which gives the thickness of strata as ascertained 

 at Reeve's clay-bank, and at the well as learned from a record 

 furnished by those interested in its boring. 



Surface gravel 5 ft. 



Yellow clay 8 ft. 13 ft. 



Ferriferous clay and ironstone crust 4 ft. 17 ft. 



Fossiliferous black sand, containing Ammo- 

 nites, Scaphites, Baculites and other Mol- 

 lusks 3 ft. 20 ft. 



Black clay 44 ft. 64 ft. 



(A) Fine and coarse gray sands at the top, 

 changing to medium and then to coarse 



and pebbly gravels at the bottom 33 ft. 97 ft. 



Green sand marl 6 ft. 103 ft. 



(B) Fine, gray sand and coarse gravely simi- 

 lar to A 27ft. 130ft. 



White clay 100 ft. 230 ft. 



Red clay 10 ft. 240 ft. 



Alternations of sand and clay, sometimes 



reddish 20 ft. 260 ft. 



