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Show 1896.] OF THE PALEOZOIC OPHIUROIDEA. 1039 wings are thin. The adambulacral plates are triangular and each of them bears several spines. The pores for the podia occur at the middle of the lateral margin of the ventral arm-shields. Distribution.-Lower Devonian, Bundenbach. Type species.-Eoluldla clechenl, Stiirtz, 1886. Genus 2. EOSPONDYLUS, nov. gen. Diagnosis.-Disc circular. Ambulacral ossicles completely fused into vertebral ossicles, each of which, however, is traversed by a pore. The adambulacral ossicles are somewhat pear-shaped. The podial pores are at the posterior angles of the ventral arm-plates. Distribution.-Lower Devonian, Bundenbach. Type species.-Eospondylus prlmlgenla (Stiirtz), 1886 [15. p. 77]. Genus 3. MIOSPONDYLUS, nov. gen. Diagnosis.-Disc circular. Ambulacral ossicles completely united; each half of the vertebral ossicle is boot-shaped. The oral angles each consist of a pair of syngnaths without jaw-plate. The ventral arm-plates are small, and are not notched by podial pores. Distribution.-Lower Devonian, Bundenbach. Type species.-Miospondylus rhenanus (Stiirtz), 1893 [17. p. 29, pl. i. figs. 1-3]. Remarks.-The two genera Eospondylus and Miospondylus are both founded on species described by Stiirtz, and included by him in Ophlura. It is impossible that they can remain in this genus, and Stiirtz, no doubt, only placed them there provisionally. They agree in family characters with Eoluldla, but differ from it in the structure of both the ambulacral and adambulacral plates. The differences between them would certainly rank as of generic value among recent Ophiurids. To leave the two species in Eoluldla would only encourage the neglect of specific characters and a looseness of description which has already greatly retarded the study of the fossil Ophiurids. Genus 4. AGANASTER, Miller & Gurley, 1890. Syn. Ophlopege, Bohm. This genus was proposed by its authors to include a species described as Protaster gregarlus by Worthen and Meek. It has nothing to do with Protaster and is clearly a member of the Streptophiurae. As far as its characters are known to m e it must be included among the Eoluididae. It differs from the rest of this family by the presence of dorsal arm-plates. Without the opportunity for the examination of more specimens than there are in the British Museum, I do not care to attempt a new diagnosis. Improvements on the original diagnosis of Miller and Gurley must be left to American palaeontologists. P R O C ZOOL. Soc-1896, No. LXVII. 67 |
