LAMELLIBEANCHIATA OF THE LOWEE MARLS. 39 



ties of the lower and middle green sands of the New Jersey Cretaceous, but 

 they all appear to have been collected with but httle care and without any 

 discrimination as to their exact position as regards their stratigraphical rela- 

 tions to the different layers of the formation, so that it is practically impos- 

 sible to assign any one variety its definite localities or horizon, and this 

 may be said of the majority of all the collections of invertebrate fossils 

 wdiich I have seen from within the State. In fapt, to so great an extent is 

 this the case that I find it absolutely unsafe to credit many of the localities 

 which I find assigned to specimens, while by far the greater part are only 

 known as having come from New Jersey, and many others entii^ely without 

 locality mark of any kind. But little true progress in the study of the Pale- 

 ontology of the State can be made until collections shall be made with care, 

 and accurate lists of the species from each particular bed given from the 

 various localities. The form G. navia has been received from Professor Cook 

 as coming from Monmouth County, and from Blue Ball, N. J.; the G. naviceUa 

 from Blue Ball and Monmouth, New Jersey.. I also know it from Freehold 

 and Burlington, in the lower beds, and from Timber Creek and New Egypt, 

 in the middle beds. It is also known to occur at Barrie Bluff and elsewhere 

 in Alabama and in Texas, and is common at many places in Europe. The 

 ordinary form of G. convexa is known from Monmouth, Cream Ridge, New 

 Egypt, Harrisonville, near Mullica Hill, and elsewhere in New Jersey. 



The form described under the name . Pycnodonia mutahiUs is marked 

 Monmouth Count}^, in Rutgers College cabinet. I have seen it at Cream 

 Ridge in company with G, convexa, and the form shown on PL IV, Fig. 3, is 

 without local distinction. 



Genus EXOGYEA Say. 

 Exogyra costata. 



Plate VI, Figs. 1 and 2. 



Exogyra costata Say. J. A. N. S. Phil., 1st series, Yol. II, p. 43. Also of rnauy authors. 

 Ostrea Americana Desh. Enc. Method. Vers., Yol. 11, p. 304, ]^o. 45 {Gryphcea), Lam., 



Anim. sans Yert. (Desh. ed.), Yol. YII, p. 207 (Meek). 

 ? 0. torosa Mort. Synop., p. 52, PI. X, Fig. 1. 



Shell large, thick, and ponderous, irregularly circular or subovate in 

 outline, plano-convex in profile and obliquely coiled at the apex, the lower 



