THE MISSISSIPPIAN PERIOD. 525 



in the fauna, and some of their species had a wide geographic range, 

 extending to the eastern continents. Some of the typical forms 

 are illustrated in Fig. 236, l-t. The molluscan factor was subordinate. 

 A few winged pelecypods, a few capulid gastropods, an occasional 

 pteropod, and an even rarer cephalopod, make up the poor repre- 

 sentation of this class. The low estate of the cephalopods, so promi- 

 nent earlier, and to be so again later, is very notable. They were 

 represented chiefly by the Nautilus family. 



There were a few lingering trilobites and some other crustaceans, 

 a quite ample growth of bryozoans of much interest, some supposed 

 sponges (Fig. 236, v and w), and doubtless the less easily fossilized 



Explanation of Fig. 23G. — Crinoidea: a, Barycrinus hoveyi Hall, one of the 

 fistulate, inadunate crinoids, note the persistence of the uniserial arm struc- 

 ture; b, Dorycrinns missouriensis (Shum.), a camerate crinoid of the family 

 Batocrinidae; note the peculiar development of the basal plates and the 

 spinose plates-of the vault; c, Forbesiocrinus wortheni Hall, one *of the flexi- 

 ble crinoids; d, Lobocrinus longirostris , (Hall), one of the Batocrinidae, showing 

 the extravagant development of the anal tube; the arms are removed; e, Syn- 

 bathocrinus wortheni Hall, one of the larviform inadunate crinoids; note the small 

 cup and the simple, uniserial arms; /, Platycrinus verrucosus White, and g, Platy- 

 crinus gorbyi S. A. M.; Platycrinus is one of the conspicuous Osage genera; these 

 two figures show different types of ornamentation; h, Actinocrinus lobatus Hall; note 

 the high degree of ornamentation of the plates; i, Eretmocrinus remibrachiatus 

 (Hall), a representative of a genus of the Batocrinidce characterized by the peculiar 

 spatulate arms. Blastoidea: j, Orophocrinus stelliformis (0. and S.), one of the 

 lower Osage blastoids. Echinoidea: k, Oligoporus mutatus Keyes. All o£ the 

 Palceechinoidea to which sub-class all Mississippian and Carboniferous sea urchins 

 belong, have more than two rows of plates in each ambulacral and interambulacral 

 area. Brachiopoda: I, Syringothyris subcuspidatus (Hall); the genus of which 

 this is a representative is an offshoot from Spirifer, characteristic of the Mississippian 

 faunas; it is characterized by its high area, punctate shell structure, and a pecu- 

 liar tube between the dental plates; m, Spirifer logani Hall, the American repre- 

 sentative of the Spirifer striatus of the European Mountain Limestone fauna; 

 note the large size, the completely plicated shell, with the plications bifurcating 

 on both the fold and on the sides of the shell. The surface is marked by very 

 fine striae not shown in the figure; n, Spirifer suborbicularis Hall, another type 

 of spirifer, closely allied species of which occur in America and Europe; o, Retic- 

 ularia pseudolineata (Hall), one of the spire-bearing brachiopods having a closely 

 allied species in the European Mountain Limestone fauna; p, Athyris lamellosa 

 L'Eveille, a species which occurs both in America and in Europe; q, Productus 

 burlingtonensis Hall, one of the species of this peculiarly Mississippian, Car- 

 boniferous and Permian genus, which occurs abundantly in the lower Osage; r, 

 Leptcena rhomboidalis Wilck, a species which has persisted from Ordovician times, and 

 which appears for the last time in the Osage fauna; s, Rhipidomella burlingtonensis 

 (Hall), and t, Schizcphoria sivallovi Hall, two species which are among the last 

 representatives of the orthids, a family whose great development was in the Ordo- 

 vician; both species have near relatives in the European Mountain Limestone 

 faunas. Coral: u, Zaphrentis centralis E. and H. , the most characteristic coral 

 of the Osage faunas. Sponge: v-w, Palwacis obtusum M. and W. The exact nature 

 of this fossil is not well understood. It is usually placed with the sponges, although 

 by some it is included with the corals. (Weller.) 



