372 PROCEEDINGS OF THE ACADEMY OF 



This beautiful little species, which was first pointed out to me by my friend, 

 Dr. Horn, occurs in a rich fossiliferous marl, associated with numerous species 

 of Polyzoa, and some larger mollusca, and is not uncommon. The measure- 

 ments given above are from the largest specimen. It appears to be full 

 grown. It differs from M. anomioides Scacchi, as figured by H. and A. Adams, 

 in being more rounded in outline, never nearly so quadrate, and in wanting en- 

 tirely the basal emargination, although, in some specimens the lower margin is 

 faintly undulated, showing a tendency to form a median sinus. 



CARBONIFEROUS. 



GONIATITES. 



G. e n t o g o n u s. Robust, discoidal ; whorls six or seven, gradually in- 

 creasing in size, each one embracing about two-thirds of the preceding volution. 

 Umbilicus broad, making about a third of the diameter of the shell. Hody 

 whorl broadly rounded on the dorsum-, widest at the umbilical margin, which 

 is bordered by a sharp angular ridge, inside of which the surface slopes to the 

 preceding whorl with a very slight convexity. The cast is marked by about five 

 depressions on each whorl, the remains of periodical, thickened lips, which are 

 nearly straight in the younger state, but are slightly sinuous in the larger 

 specimens. Septse placed closely, so that the extremities of the saddles are 

 within the line of the ends of the lobes of the preceding septum. There are 

 two lobes and two saddles on each side besides the dorsal lobe. Dorsal lobe 

 long, sides nearly parallel, extremity doubtful (probably bifid) ; dorsal saddle 

 wider than the lobes ; sublingmeforni and acuminate in the middle ; superior 

 lateral lobe of about the same size as the dorsal saddle, but somewhat wider at 

 its commencement and rounded at the extremity ; lateral saddle differs only 

 from the dorsal in being wider; latero-ventral lobe very oblique, with its inter- 

 nal edge extending to the carinated margin of the umbilicus. 



Diameter, 2 25 inches ; height of mouth, -5; width of mouth, 1-2 in. ; height 

 of body whorl, -9 in. 



From the carboniferous limestone of Lampases Co., Texas, immediately un- 

 derlying cretaceous rocks. State collection, Austin, Texas. 



This species is most nearly related to G.Owenii Hall, and G. Hi/as ej. It dif- 

 fers from the former in having a broader umbilicus than is shown in the figure 

 of that species (13th Report, Regents N. Y. Univers., p. 100,) and in the addi- 

 tional lobe to the septum. The whorls are broader and more embracing than 

 those of G. Hyas; the septum has the same number of lobes, but they are of a 

 different shape, the extremities being rounded, while the extremities of the saddles 

 are pointed, being just the reverse of the arrangement in that species. The late- 

 ro-ventral lobe of the present species is very oblique, especially on the ventral 

 side, and the corresponding saddle is almost absent, while in G. Hyas this lobe 

 differs only from the lateral one in size and the ventral saddle is distinctly 

 marked. The carinated edge to the umbilical margin of the body whorl will 

 also serve as a strong distinguishing character. 



Associated with this species is the mutilated cast of a large species of Belle- 

 rophon, which I cannot identify with any known species. I am indebted to my 

 friend, Dr. Moore, State Geologist of Texas, for the privilege of studying this 

 and many other interesting fossils collected in that State. 



Notes on certain Decapod Crustacea. 

 BY WM. STIMPSON. 



Pachygrapsus marmoratus. 



Cancer marmoratus Fabr. ; Herbst. 



Grapsus variits Latr. ; M. Edw. 



Leptograpsus marmoratus M. Edw. Melanges Carcinologiques, p. 137. 



[Nov. 



