File:North American index fossils, invertebrates (1909) (14594401110).jpg

Identifier: northamericanind02grab (find matches)
Title: North American index fossils, invertebrates
Year: 1909 (1900s)
Authors: Grabau, Amadeus W. (Amadeus William), 1870-1946 Shimer, Hervey Woodburn, 1872-1965
Subjects: Paleontology Invertebrates, Fossil
Publisher: New York : A.G. Seiler
Contributing Library: California Academy of Sciences Library
Digitizing Sponsor: California Academy of Sciences Library

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enter of top and bottom of test and singleat the ambitus. Jurassic and Cretacic.21. D. texana (Roemer). (Cyphosoma texanum.) (Fig. 1921, a^d.) Comanchic. Large, with inflated sides. Lower surface concave. Pores insingle pairs from mouth to ambitus (except immediately border-ing the mouth) beyond which to the apex they are in double rows.Periproct large, subpentagonal. Comanche-Peak (Fredericksburgian) of Texas. XIV. Pedinopsis Cotteau. Differs from Diplopodia in having more than one tubercle onambulacral plate, and numerous smaller tubercles on interambu- 588 NORTH AMERICAN INDEX FOSSILS. lacral. Large, round, ventricose, sometimes subconical; ambulacralpore-belts straight, broad, with a simple paired row of doublepores on the under side; tubercles small, with median perforationand crenulated. Comanchic-Cretacic. 22. P. pondi Clark. (Fig. 1921, ^-^.) Cretacic. Under surface flattened, with a slight concavity near the region of the mouth opening; ambulacra with six rows, and interambu-
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FiG. 1921, a-d^ Diplopodia iexana: a, upper surface; b, side view; r, lowersurface of smaller individual, all X M > ^> ambulacral area enlarged ; e~g, Pedinopsispondi: Si ambulacral plates enlarged.(After Clark.) lacra with twenty rows of tubercles at the ambitus; tuberclessmall, equal, crenulated and perforated; peristomial opening small,with distinct incisions. Austin Chalk (Niobrara) of Texas. ECHINODERMA TA—ECHINOIDEA. 589 XV. Cyphosoma Agassiz. Test depressed, highly ornamented. Ambulacra with well-developed pore-bearing zones, undulating, and each plate with threeto seven pairs of pores in an arc. Pairs of pores in two rows atthe apex and crowded at the mouth opening. Interambulacra withtwo or more vertical rows of primary tubercles which are imper-forate and crenulate, like those of the ambulacra. Apical systemencroaching upon the posterior interambulacrum. Jurassic-Recent. 23. C, volanum Cragin. Comanchic. Small, similar

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