<iAHK.| TltEMATUPYGUS CKUCIFEK. 63 



The iuterambulacral platos are largo and covered with irregnhirly 

 arranged tubercles. Between the tubercles a microscopic granulation 

 covers the surface {V\. xxvi, Fig. 1/). 



The apical disk is small and situated forward of the apex. The indi- 

 vidual plates can not be fully distinguished on the specimen examined. 

 The mouth opening is apparently small, though somewhat obscured. 

 It is situated forAvard of the center of the base. 



The anal opening is small, placed in a narrow sulcus that begins scmie 

 distance posterior to the. apical disk. 



Related forms. — Uehinobrusus texanus is readily separated from E. 

 exjxoisus by its ovate form and the shape and size of the anal sulcus. 

 It is uulike any European species. 



Locality and geological horizon. — This form is from the Austin chalk 

 (upper Cretaceous) of the south bank of the Colorado river, Austin, 

 Texas. 



Collection. — U. S. National Museum. 



TREMATOPYGUS d'Orbigny. 



Trematopygus crucifer (Morton). 



Plate XXVII, Figs. la-*. 



Anancliyies cniciferus Mortou, 1830. Am. Jour. Sci.. let ser., vol. 18, p. 245, PI. 3, 

 Fig. 8. 



Ananchijtes cruciferus Morton, 1830. Philadeliiliia Acad. Nat. Sci.,l8t ser., vol. 6, pp. 



201, 202. 

 'Nudeolites o-Mci/cr Mortou, 1833. Am. Jour. Sci., 1st ser., vol. 23, p. 294. 



NiideoViies crucifer Morton, 1834. Synop. Organ. Kemaius, Cretaceous, p. 75, PI. 3, 

 Fig. 15. 



Nticleolites criiciferua Agassiz, 1840. Cat. Syst., p. 4. 



NiicleoUtcs cruciferus d'Orbiguy, 1847. Prodrome, vol. 2, p. 271, fitage 22, No. 1197. 

 ■ NuclcoUtes cruciferus Agassiz and Desor, 1847. Cat. rais., p. 97. 

 -Xuclcolites crucifer Broun, 1848. Index Pal., vol. 1, p. 818. 



Pi/fjorhynchus crucifer Kavenel, 1850. Am. Assoc. Adv. Sci. I'roc, p. 100. 



Xrematopiifjus crucifer d'Orbigny, 1853-'60. Palcont. fran^aise, vol. 6, p. 387, PI. 953, 

 Figs. 10, 11; PI. 963, Figs. 1-5. 



Echinobrissus cruciferus d'Orbigny, 1854. Revue zool., p. 25. 

 .Nudeolites crucifer Desor, 1858. Synop. des l^chinides fossiles, p. 262. 

 ■Nudeolites crucifer Gabb, 1859. Cat. Invert. Fossils Cretaceous, p. 19. 

 ■Nuct^oUtes crucifer Meek, 1864. Smith Misc. Coll., vol. 7 (177), p. 2. 



Nudeolites crucifer Cook, 1868. Geol. of New Jersey, p. 377. 



Nudeolites crucifer Conrad, 1868. Geol. of New Jersey, Ai)p., p. 722. 



■Nucleolites cruciferus Credner, 1870. Zeitscbr. d. deutsch. geol. Gesells., xxii, p.217. 



Trcmatopiigus crucifer Clark, 1891. Johns Hopkins University Circulars, No. 87, p. 76. 



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

 and slightly contracted anteriorly. Aubulacra long, well defined ; pores 

 unigeminal, prominent on the upper surface, indistinct on the base. 

 Apical disk situated anteriorly. JMouth oix'uing large and oblique. 

 Anal opening large, oval, supramarginal. 



Dimensions. — Length, 1 iiu'h; breadtli, I inch; height, j-,;- inch. 



Description. — This urchin is not uncommon at Timber creek. New 

 Jersey, where many yery perfect specimens have been obtained. Its 



