92 MESOZOIC ECHINODERMATA OF THE UNITED STATES. [bull. 97. 



are broad and straight. The pores are large and oval, and those of 

 each pair connected by a shallow furrow (PI. l, Fig, 1/). The antero- 

 lateral i^etals reach far down the sloping sides and are about one and 

 one-half times as long as the posterolateral pair. 



The surface of the test is covered with minute, perforated tubercles 

 that are much larger on the base than on the upper surface. A micro- 

 scopic granulation fills the space between the tubercles (PI. l, Fig. li). 

 Both the peripetalous and lateral fascioles can be readily traced. 



The apical disk is small, nearly central, and slightly depressed (PI. 

 L, Fig. Ig). 



The mouth opening is transversely oval and situated near the 

 anterior margin. The anal opening is small, oval, and situated but a 

 short distance above the posterior margin (PI. l,, Fig. Id). 



Belated forms. — L. tumidnla is the only representative of the genus 

 from American deposits. It is not closelj^ allied to any species de- 

 scribed elsewhere. 



Locality and geological horizon. — Linthia tumidnla is from the yellow 

 limestone of the middle marl bed (upper Cretaceous), of Timber creek, 

 New Jersey. 



Collections. — American Museum of Natural History, New York; Bos- 

 tonSociety of Natural History. 



DOUBTFUL AND UNRECOGNIZED SPECIES. 



With few exceptions the writer has had an opportunity of examining 

 the type forms of previous writers upon the Mesozoic Echinodermataof 

 the United States, and as a result Cassidvlns abruptns Conrad, Arhacia 

 sp. Eoemer, and Diadema sp. Poemer are the only species that can not 

 be identified. Three other species — two from lack of generic charac- 

 ters {Pygnrus {?) geometricus (Morton) and Gidaris nahalalcensis de 

 Loriol), the third {Discoidea occidcntale (labb) because of probable 

 foreign origin — are not included, although the synonjnny of each is 

 given for imri)oses of reference. A single specific name {Holectypus 

 simplex Roemer) has found its way into the literature from its use in 

 Gabb's Catalogue, although i)robably mentioned by mistake. 



Cassidttlus abritptus Conrad. 



Cassidtilus abrnpiiin Conrad, 18G0. Pbiladeliihia Acad. Nat. Sci. Jour., new ser., vol. 4, 



p. 291. 

 Cassichilns abriiptns Clark, 1891. Johns Hopkins University Circulars, No. 87, p. 77. 



This species, originally described by Conrad in ISGO, but not figured, 

 is from Tippah county, Mississippi. It has not been recognized in 

 material examined by the writer, so that its relations to the other forms 

 described are not known. 



Pygubus C?) GEOMETRICUS (Morton). 



Clypeaster sp. Morton, 1830. Philadelphia Acad. Sci. Jour., 1st ser., vol. 6, p. 202. 

 Clypeaster geometricm Morton, 1833. Am. Jour. Sci,, 1st ser., vol. 24, p. 131, PI. 10, 

 Fig. 9. 



