272 MR. J. A. DOr&LAS 0>'' GEOLOGICAL SECTIONS [vol. Ixxvii, 



Palaeontological Note. 



ExALLASTEE TEXANUS (Eoemer) = E. PEEUAxrs Gabb. 



The PeniYian form orig'inally described by Gabb ^ is probably identical 

 \vith F. Eoenier's Xortli- American species. - 



A closely-allied species is also that described from Mexico by Dr. Bose, as 

 Enallaster hniroensis.^ Many of these figures agree in essential details with 

 those of PeriiTian fossils illnstrated by L. Sommermeier."^ 



HoLECTTPUs PLANATUS Eoemer. 



Two distinct forms of this shell are represented in my collection. The first 

 agrees closely with the type illustrated by Eoemer ^ and appears to be closely 

 related to Dr. E. Bo5e"s Mexican species. Holectypus Umitis.^ The second, 

 from the limestones of Tauli, which appear to lie below the Albian ammonite- 

 beds, was never found in conjimction with any of the species mentioned in the 

 above Kst, and is probably identical with the variety figured by Sommermeier 

 as J3". pJanafus'Rcem.ev var, numismaUs (Gabb)," although the original speci- 

 men figured by Gabb is a much larger form.^ The two forms, therefore, may 

 eventually prove to be distinct species. 



LiopiSTHA (Psilo-MTA) gigaxtea (Sowerby). 



A very characteristic shell occurring in g-reat abundance, and agreeing 

 closely with Sowerby's type from the Upper Greensand of Blackdown (zone 

 of Scidcenhaclxia rostrate.) as figured by Mr. H. Woods. ^ 



ExoGYEA c/. coxiCA Sowerby. 



Large specimens of this shell, which possibly represents a late mutation of 

 Sowerby's species, were found at a somewhat higher horizon than that of the 

 echinoderm-beds. Their position, therefore, is analogous to that of the large 

 Mexican form, Exogyra ponderosa. although the two species are quite distinct. 



The following table gives a suggested correlation of the Creta- 

 ceous rocks of the Orova disti'ict with, those described bv Dr. Bose 

 from the Cerro de Muleros (^Mexico). It is intended to show the 

 similarity of the faunal assemblages in tlie two areas, but must not 

 be taken to indicate that the species are regarded in every case 

 as being identical. The subdivisions are those recognized bv 

 Dr. Bose :— 



^ See Bibliography, § IT. Xo. 40, vol. viii. p. 301 & pi. xliii, figs. 4-4 c. 



- ' Die Kreidebildungen von Texas & ihre Organischen Einschliisse ' 1852, 

 p. 8.5 & pi. X. fig. 3 : see also TV. B. Clark, ' The Mesozoic Echinodermata 

 of the Tnited States ' BuU. U.S. Geol. Surv. 97 (1893) p. 78 & pi. xxxix, 

 figs. 2 a -2 g. 



^ ' MonogTafia Geologica & Paleontologica del Cerro de Muleros ' Bol. Inst 

 Geol. Mex. 25 (1910) pi. xli. figs. 5-10. pi. xlii. figs. 2-12, & pi. xliii. figs. 1 

 2, 6, 7. 



"^ Bibliography, § lY, Xo. 52, pi. xv, figs. 4-6. 



^ Op. cit. pi. X, fig. 2 c. 



^- Op. cit. pi. xxxvi, figs. 3-6 & pi. xxxvii, figs. 1-S, p. 159. 



^ Op. cit. pi. XV. figs. 1-3 ~ Discoicleal. 



8 BibHography, § IV, Xo. 40. pi. xlLrf, figs. 3-3 6. 



^ ' Cretaceous Lamellibranchia of England ' Palgeont. Soc. Monogr. vol. ii 

 (1913) p. 257 & pi. xliii, figs. 3-4, pi. xliv, figs. 1-2. 



