CRETACEOUS ECHINODERMATA. 71 



Genus TREMATOPYGUS D'Orbigny. 

 Trematopygus cruciferus (Morton). 

 Plate XXVIII, figures 3a-c; Plate XXIX, figures la-f. 



-Ananchytes cruciferus Morton, 1830, Am. Jour. Sci., 1st ser., vol. 18, p. 245, PL III, fig. 8. 

 Ananchytes cruciferus Morton, 1S30, Acad. Nat. Sci. Philadelphia Jour., 1st ser., vol. 6, pp. 201, 202. 

 Nucleolites crucifer Morton, 1833, Am. Jour. Sci., 1st ser., vol. 23, p. 294. 



Nucleolites crucifer Morton, 1834, Synopsis Organic Eemains Cretaceous, p. 75, PI. Ill, fig. 15. 

 -Nucleolites cruciferus Agassiz, 1840, Catalogus systematicus, p. 4. 

 Nuculites cruciferus Agassiz and Desor, 1847, Catalogue raisonne, p. 97. 

 Nuculites crucifer Bronn, 1S48, Index palasontologicus, vol. 1, p. 818. 

 Nucleolites cruciferus D'Orbigny, 1S50, Prodrome, vol. 2, p. 271, etage 22, No. 1107. 

 Pygorhynchus crucifer Ravenel, 1S50, Am. Assoc. Adv. Sci. Proc, p. 160. 

 Trematopygus crucifer D 'Orbigny, 1853-60, Paleontologie francaise, vol. 6, p. 3S7, PI. CMLIII, figs. 10, 11 ; PL CMLXIII, 



figs. 1-5. 

 Echinobrissus crucifer D 'Orbigny, 1854, Rev. etmag. zoologie, ser. 2, vol. 6, p. 25. 

 Nucleolites crucifer Desor, 1858, Synopsis des echinides fossiles, p. 262. 

 Nuculites crucifer Gabb, 1S59, Cat. Invert. Fossils Cretaceous, p. 19. 

 Nuculites crucifer 'Meek, 1864, Smithsonian Misc. Coll., vol. 7 (177), p. 2. 

 Nuculites crucifer Cook, 1868, Geology of New Jersey, p. 377. 

 Nuculites crucifer Conrad, 186S, Geology of New Jersey, App. A, p. 722. 

 Nuculites cruciferus Credner, 1870, Deutsche geol. Gesell. Zeitschr., vol. 22, p. 217. 

 Trematopygus crucifer Clark, 1891, Johns Hopkins Univ. Circ, vol. 10, No. 87, p. 76. 

 Trematopygus crucifer Clark, 1S93, John:.; Hopkins Univ. Circ, vol. 12, No. 103, p. 52. 

 Trematopygus crucifer Clark, 1S93, U. S. Geol. Survey Bull. 97, pp. 63, 64, PI. XXVII, figs. la-i. 

 Trematopygus crucifer Johnson, 1905, Acad. Nat. Sci. Philadelphia Proc, vol. 57, p. 7. 

 Trematopygus cruciferus Veller, 1907, Cretaceous paleontology of New Jersey: Geol. Survey New Jersey, pp. 2S9-290, 



PL XI, figs. 1-9. 



Determinative characters. — Test ovate, inflated at the sides and base and slightly con- 

 tracted anteriorly. Ambulacra long, well defined ; pores uniserial, prominent on the upper sur- 

 face, indistinct on the base. Apical system situated anteriorly. Peristome large and oblique. 

 Periproct large, oval, supramarginal. 



Dimensions. — Length 18 to 20 millimeters; breadth 15 to 22 millimeters; height 10 to 14 

 millimeters. 



Description. — This species is not uncommon at Timber Creek, N. J., where many very perfect 

 specimens have been obtained. Its outline is ovate and very regular, lacking at the ambitus or 

 apex any sharply defined angularity. The sides are highly inflated together with the outer 

 portion of the base. 



The ambulacra are long, lanceolate, and unequal; the posterior pair are the longest, the 

 impaired anterior one is the shortest. They do not produce any irregularity in the outline of 

 the test beyond inconsiderable dejDressions in the immediate vicinity of the peristome. The 

 poriferous zones are clearly marked on the upper surface, and the pore pairs are nearly horizontal, 

 but toward the ambitus the pores become smaller, those of each pair nearer together, and the 

 pairs obliquely situated at the lower, outer corner of each'plate; near the peristome they again 

 become larger and slightly increased in number. 



The interambulacra are wide and composed of large plates that are bent in the middle. 

 The surface is covered with irregular rows of tubercles that are perforated and mammillated. 

 The miliary space is covered with numerous minute and irregularly distributed granules. 



The apical system is small and anteriorly situated; the four genital plates are distinctly 

 perforated ; those of the anterior pair are much nearer together than those of the posterior. 



The peristome is large, oblique, and placed somewhat forward of the center of the base. 

 The periproct is large, oval, and acuminate at the upper extremity. It is situated in an anal 

 sulcus that makes a marked indentation in the posterior margin, and is bordered by two well- 

 defined ridges. 



Related forms. — Trematopygus cruciferus (Morton) is a unique species that has no closely 

 allied forms in either American or European deposits. 



