230 PROCEEDINGS OF THE NATIONAL MUSEUM vol.84 



the apices of the pentagon, flattened dorsally, slightly reentrant about 

 the peristome, otherwise very nearly flat ventrally. Ambulacra 

 wide, measuring about 25 mm in width at the ambitus, ambulacral 

 plates composed of three elements, but tliis species, like the Recent 

 S. variolaris (Lamarck), has a peculiar arrangement in that every 

 fourth ambulacral plate bears a large primary tubercle that has grown 

 over four plates and hides their sutures. This, with other important 

 details in regard to the Recent species, is considered by Dr. H. L. 

 Clark.* Interambulacra with two vertical rows of primary tubercles 

 in each half-area. Diameter of the specimen 81 mm, height 38 mm. 



The single known specimen (U.S.N.M. no. 496275) of this new and 

 interesting ecliinoid is much worn and shows structural detail only in 

 parts of the test. The peristome and periproct are not preserved, or 

 are not \asible. The test is thick and solid and gives no evidence of 

 flattening or other distortion. 



The genus Stomopneustes is known from the Recent species ^S*. 

 variolaris (Lamarck) from the southern Pacific Ocean. According to 

 Duncan,^ a species has been found in the Tertiary of Java, but he 

 queried the statement. 



OUgocene, Mes6n, Hacienda Tierra Amarilla, about 7 km north- 

 west of the town of Temapache, Canton Tuxpan, Veracruz, Mexico; 

 Corona collection, no. 29 ( = H176), one specimen. 



Order EXOCYCLOIDA Jaekson 



Suborder Clypeastrina Gregory 



Family CLYPEASTRIDAE Agassiz 



Genus CLYPEASTER Lamarck 



CLYPEASTER MERIDANENSIS Michelln 



Clypeaster meridanensis Michelin, R^v. et Mag. Zool., ser. 2, vol. 2, p. 240, 1850; 

 M6m. Soc. Geol. France, ser. 2, vol. 7, p. 136, pi. 14, figs, la-f, 1861. 



Of the species Clypeaster meridanensis, described by Michelin from 

 the Tertiary of Merida, Yucatan, there is a fine series of extremely 

 well preserved specimens from Tuxpan, Tampico, and Hacienda Santa 

 F6, Topila, Mexico. The largest specimen, from a small quarry in 

 the town of Tuxpan, collected by D. R. Semmes, no. 82, measures 160 

 mm in length, 142 mm in width at the widest part through ambulacra 

 II and IV, and 27 mm in height. 



There are 12 specimens of this species from the Miocene of Tuxpan, 

 Veracruz, Mexico, and two from the Oligocene Meson formation of 

 Hacienda Santa F^, Topila, Veracruz. Also there is a 4-rayed speci- 

 men and a fragment from 1 mile north of Tampico and on the opposite 



• Mem. Mus. Comp. Zool., vol. 34, no. 2, 1912. 



• Revision of the genera and great groups of the Echinoidea. Journ. Linn. Soc. London, Zool., vol. 23, 

 pp. 1-311, 1889. 



