64 MESOZOIC ECHINODERMATA OF THE UNITED STATES. [buu,. 07. 



outline is ovate and very regular, lackiug- at tlie ambitus or apex any 

 sharply detiued augularity. The sides are highly inflated, together 

 with the outer portion of the base. 



The anibulacral areas are h)ug, lanceolate, and unequal; the posterior 

 pair are the longest, the unpaired anterior area is the shortest. The 

 areas do not produce any irregularity in the outline of the test beyond 

 inconsiderable depressions in the immediate vicinity of the mouth edges. 

 The poriferous zones are clearly nuxrked on the upi)er surface, and the 

 pore pairs are nearly horizontal (PI. xxvii. Fig. 1/), but toward the 

 ambitus the pores become smaller, those of eacli pair nearer together, 

 and the pairs obliquely situated at the lower, outer corner of each i>late 

 (PI. XXVII, Fig. le); near the mouth edges they again become larger and 

 slightly increased in number. 



The interaiubulacral areas are wide and comj)osed of large plates 

 that are bent in the middle. The surface is covered with irregular 

 rows of tubercles that are x)erforated and mammillated. The miliary 

 space in its turn is covered with numerous minute and irregularly dis- 

 tributed granules. 



The apical disk is small and anteriorly situated; the four genital 

 plates are distinctly perforated, those of the anterior pair situated much 

 nearer together than tliose of tlie posterior (PI. xxvii, Fig. 1//). 



The mouth opening is large, oblique, and placed somewhat forward of 

 the center of the base. The anal opening is large, oval, and acuminate 

 at the upper extremity. It is situated in an anal sulcus, tliat makes a 

 marked indentation in the posterior margin, and is bordered by two 

 well defined ridges (PI. xxvii, Fig. 1(7). 



Related forms. — TremaiopyguH erneifer (JMorton) is a unique species 

 that affords no closely allied forms in either American or European 

 deposits. It is the single representative of this genus recorded from 

 American strata. 



LocalUy and geological horizon. — The only specimens of this form 

 thus far reported are from the yellow limestone of the middle marl 

 bed (upper Cretaceous) of Timber creek, New Jersey. 



Collections. — American Museum of Natural History, New York ; Phila- 

 delphia Academy of Natural Sciences; Johns Hojikins University. 



CATOPYGUS Agassiz. 



Catopygus oviformis Conrad. 



Plate XXVII, Figs. 2a-/. 



Catopygus oviformis Conrad, 1847. Philadelphia Acad. Nat. Sci. Jour., 2d ser., vol. 



2, p. 39, PI. 1, Fig. !). 

 Nudeolites ovifornm (Cato]).vgus) Conrad, 1808. Geol. of New Jersey, App., p. 722. 

 Catopygus oviformis Clark, 1891. Johns Hopkins University Circulars, No. 87, p. 76. 



Determinative characters. — Test ovate, broader posteriorly; upper 

 surface nearly flat; apex posterior to apical disk. Ambulacra narrow, 

 subpetaloidal. Jnterambulacra wide ; single interambulacrum elevated. 



