LAMELLIBEANCHIATA FEOM THE MIDDLE MAEL BEDS. 203 



Formation and locality. — In the Middle Marls at Timber Creek perhaps 

 most abundantly, but also found near New Egypt and many other localities 

 in New Jersey. 



GASTROCHiENID^. 

 Genus GASTEOCH^lsrA Spengl. 



Gastrochaena Americana. 

 Plate XXVI, Figs. 17 and IS. 



OastrochcBtia Americana Gabb. J. A. N. Sci. Phil., new ser.. Vol. IV, p. 393, PI. QS, 



Fig. 20. Synopsis, p. 124. Meek, Checklist, p. 15. 

 .Polortlms Americana Gabb. P. A. N. Sci., 1861, p. 366. Meek, Check-list, p. 16. Sto- 



liczka, Pal. Indica, Vol. Ill, p. 15. 



This species was described by Mr. Gabb as follows: "Elongated coni- 

 cal; transversely wrinkled; termination of widest end, round." All we yet 

 know of the remains of it consist of the filling of the tubes, which are not 

 uucouxmon in the }ellow limestones at Timber Creek, N. J., but which 

 form extremal)^ unsatisfactory^ material for description or comparison with 

 other species. These bodies vary much in form and porportions, both in 

 length and diameter, as would be natural with the borings of any species. 

 The extreme in size, so far as I have seen them, is less than three inches in 

 length by about five-eighths of an inch in diameter at the lower end They 

 are very irregular in outline, being marked by numerous transverse wrin- 

 kles and constrictions, arising from what has been the rounded base of the 

 tube at different stages of growth, being partially absorbed or worn away 

 during the increase of the tube downwards with the increase growth of the 

 shell. Some of the casts appear almost as if septate, like an OrtJwceras, and 

 are very regularly tapering; while others are irregularly contorted and con- 

 stricted so as to resemble an irregular series of cups placed so as to project 

 beyond each other at the edges. No remains of the shell have been found, 

 or even casts of it, so that of this portion we are entirely ignorant. But I 

 think probable were a large collection of the tubes examined by carefully 

 breaking the lower or larger ends, some representation of the shell would 

 be detected. This species has been included by Gabb, Meek, and Stoliczka 



