MEXICAN FOSSIL ECHINI — JACKSON 233 



Family LAGANIDAE Desor 



Genus LAGANUM Gray 



LAGANUM LEPTUM, new species 



Plate 13, Figure 4 



Test very nearly circular, very flat and thin. Apical disk central, 

 peristome probably the same, but invisible. Ambulacral petals short, 

 wide, obovate. Poriferous areas wide. Periproct very near to, being 

 only 2 mm from, the posterior border of the test. 



The single known specimen (U.S.N.M. no. 496280) measures 38 

 mm in length, 35 mm in width, and about 5 mm in height. This 

 species approaches perhaps nearest to Laganum johnsoni Twitchell, 

 from the Eocene of Alabama. It differs from johnsoni in the extreme 

 thinness of the test and in the shortness and obovate form of the 

 petals in leptum. 



L. Upturn was collected by Dr. T. W. Vaughan in the Oligocene 

 Mes6n formation on the line of the Transcontinental Railroad, lot 

 145, Hacienda Chinampa, 8 km east of the town of Chinampa, 

 Canton Tuxpan, Veracruz, Mexico, at the first cut examined, Novem- 

 ber 28, 1920. 



Family SCUTELLIDAE Agassiz 



Genus SCUTELLA Lamarck 



SCUTELLA CAZONESENSIS Kew 



Scuiella cazonesensis Kew, Proc. California Acad. Sci., ser. 4, vol. 7, p. 132, pi. 19, 

 fig. 1, 1917. 



This species is represented by a fragmentary but very well pre- 

 served specimen of an individual almost exactly the same size as the 

 one figured by Kew. 



The specimen here considered is from La Cuesta, Soto la Marina 

 River, Corona collection, no. 28. The geologic horizon is not defi- 

 nitely know^n, but is either upper Mes6n or Tuxpan. 



Suborder Spatangina Jackson 

 Family HEMIASTERIDAE H. L. Clark 



Genus AGASSIZIA Valenciennes 



AGASSIZIA CLEVEI Cotteau 



Agassizia clevei Cotteau (pars), Kongl. Svenska Vet.-Akad. Handl., vol. 13, 

 no. 6, p. 33, pi. 6, figs. 2-8, 1875. — Jackson, Carnegie Inst. Washington 

 Publ. 306, p. 71, pi. 12, figs. 5-7, 1922. 



Not Agassizia clevei Kew, Proc. California Acad. Sci., ser. 4, vol. 7, pi. 17, figs, 

 la, lb, 1917. 



Two specimens are referred to this species. The larger of the 

 two as a variant shows considerable resemblance to A. rriflata Jackson. 



