NO. 5 RHYNCHONELLOID BRACHIOPODS — COOPER 7 



loid shell and are usually moderately long, somewhat curved plates ex- 

 tending into the body cavity. To them the body wall is attached and the 

 brachia are attached to the anterior body wall at their extremity. 

 Among the Mesozoic rhynchonelloids several distinctive types of crura 

 have been named. The five types distinguished do not cover the pos- 

 sibilities among the Rhynchonelloidea because the crura of many of 

 the Paleozoic genera have not yet been described and illustrated. Fur- 

 thermore all these types are not recognizable in the Recent and Terti- 

 ary forms. 



Rothpletz (1886, p. 86) was the first to name types of crura. He 

 distinguished the following (translated from the German) : 



1. Radulifer type. — Generally consisting of two dental plates in the 

 larger [pedicle] valve, a median septum in the small [brachial] valve, 

 two hinge plates joined at the beak of the small [brachial] valve, and 

 two narrow crura curved toward the large [pedicle] valve, which at 

 their free lower ends are provided with barbs. One can compare these 

 crura with the radula [Schabeisen] of the Greek athletes and I there- 

 fore name rhynchonellas with such crura radulifer. (Rothpletz, pi. 1 1, 

 figs. 20 and 21.) 



2. Falcifer type. — The crura, with otherwise like structures, rarely 

 have the form, as with lacunosa according to Quenstedt's researches, 

 the form of broad, sharp septa which are extended parallel with the 

 plane of symmetry of the shell and possess a sickle shape (Rhyncho- 

 ncllae falciferae). (Rothpeltz, pi. 11, fig. 19.) 



3. Septifer type. — There can be, however, such sickle-shaped crura 

 so broad they make contact with the edge directed toward the small 

 [brachial] valve, are grown with it and consequently appear like actual 

 septa extending from the shell (Rhynchonellae septiferae). (PI. 8, 

 figs. 46-48.) 



Thirty-four groups or "Sippe" of rhynchonelloids were recognized 

 by Rothpletz but the interior details of 19 of them were unknown at 

 this time. Of the remaining 15 Sippe, 3 belong to the falcifer group 

 (Trilobita, Lacunosa, and Varians), 2 belong to the septifer type 

 (In versa and Trigona), and 10 are placed in the radulifer group 

 (Amalthei, Variabilis, Concinna, Plicatissima, Tetraedra, Inconstans, 

 Difformis, Plicatella, Psittacea, and Spinosa). Some of these Sippe 

 have been made into genera but generally little relationship exists 

 between the interior details of many of the species placed in each 

 group. 



Wisniewska (1932, p. 6), in her fine work on rhynchonelloids from 



