168 



GENERA OF THE SUBORDERS ORTHOIDEA AND PENTAMEROIDEA 



and convergent, forming a cruralium duplex; short 

 alx present just anterior to the brachial supports. 



Geologic range. — Middle Ordovician (Chazy) 

 to Middle Silurian of North America. 



Species 



Camerella n. sp. 



C. volborthi Billings 1859 



Parastrofhia greenei (Hall and Clarke) 1 895 (placed here 



after a study of Hall and Clarke's figure) 

 P . hemiflicata {HnW) 1847 



P. hemifUcata rotunda (Winchell and Schuchert) 1893 

 P. rotundijormis WiUard 1928 

 P. ? scojieldi (Winchell and Schuchert) 1893 



Distinguishing characters. — Camerella as here 

 restricted is characterized by the presence of a spon- 

 dylium duplex, a cruralium duplex, and dorsal septa 

 having short alate extensions on the outside. 



Discussion. — ^The genotype selected by Hall and 

 Clarke is C. volborthi Billings, which proves to be 

 structurally identical with Parastrofhia hemiflicata 

 Hall, the type species of that genus. Both forms have 

 the same kind of spondylium and cruralium and possess 

 the ala which are so much better developed in Anastro- 

 fhia. It is evident, then, that Parastrofhia Hall and 

 Clarke 1893 (a homonym replaced by Parastrofhina 

 Schuchert and LeVene 1929) and Camerella Billings 

 1859 are synonyms, and the latter name has priority. 

 Regarding Cafnerella, Hall and Clarke say that 

 these shells have "in effect, a rhynchonelloid exterior," 

 with a well defined spondylium supported by a short 

 median septum, and an open delthyrium without del- 

 tidial plates. The cardinalia consist of "crural plates 

 converging and forming a short, very small median 

 cavity, which is supported by a long septum," and 

 this hinge structure "is similar to that of Camarotoe- 

 chia . . . The crura are short, and the lateral divi- 

 sions of the hinge-plate small. No cardinal process 

 exists. The internal structure of Camerella is, thus, 

 not unlike that of Syntrofhia, notwithstanding the wide 

 difference of exterior." 



It is evident that there is needed a revision of the 

 species commonly referred to Camerella under the 

 current conception of the genus." The present writers 

 exclude from this genus C. hella Fenton, C. ambigua 

 (Hall), C. tnornata Weller, and the following species 

 of Billings: C. varians, C. longirostris, C. fanderi, 

 C. costata, C. folita, and C. farva. Some of these 



" For the early Middle Ordovician (Chazy) shells which 

 have usually been called Camerella, but which have a differ- 

 ent internal structure, we proposed the name Rhyncho- 

 camara in our "Synopsis" of 193 1, and left the genus under 

 the family Camerellids. We are now convinced that it is 

 in reality a rhynchonellid. For the convenience of workers 

 on that group its description is amplified in the Appendix 

 to this work. 



species must be removed to entirely different groups. 

 C. tnornata Weller does not have the external form 

 of either Camerella or Rhynchocamara and should 

 probably be assigned to ? Cyclosfira. "Camerella" 

 fanderi appears from etched specimens to possess spiralia 

 and is without a spondylium, as is also C. longirostris. 

 "Camerella" ottawaensis from Paquette Rapids (pi. 16, 

 figs. 6, 9, 13) apparently belongs to Orthorhynchula. 

 In Camerella the ventral muscles are confined to 

 the spondylium as is normal for spondylium-bearing 

 shells, but in the dorsal valve internal molds show 

 clearly four adductor impressions bisected by the septum 

 of the cruralium. This must be regarded as a primi- 

 tive character and is in contrast to the Pentameridas 

 in which the muscles are enclosed by the septal plates 

 or are confined to the cruralium. In the Camerellidae 

 the cruralium is the base of attachment of the diductor 

 muscles. 



Genus BRANCONIA Gagel 1890 



(Compare with C amerella) 



Gagel, Beitr. z. Naturkunde Preuss. hrgb. von d. Physik.- 

 Oekonom. Gesell. z. Konigsberg, vol. 6, 1890, p. 62, 

 pi. 4, fig. 12. 



Hall and Clarke, Pal. N. Y., vol. 8, pt. 2, 1893, p. 223. 



GENOHOLOTyPE. — B. borussica Gagel 1890. 



Description (translation from Gagel). — Outline 

 transversely lengthened, ventral valve (? dorsal) 

 strongly arched, provided with a thick, keel-like ele- 

 vated fold, which is divided in the middle by a low, but 

 definite groove. On the anterior margin the ventral 

 (dorsal ?) valve is provided with a deep indentation; 

 the beak is small but so strongly incurved that it touches 

 the dorsal valve and no foramen can be perceived. 

 Hinge margin somewhat narrower than the greatest 

 shell width, slightly curved. Dorsal valve (? ventral) 

 flattened, with a small beak, from each side of which 

 there runs a small flat surface that joins with the shell 

 proper at an angle. Close under the beak begins a 

 very deep, steep sinus; at the anterior margin the dor- 

 sal valve is drawn out into a rather noticeable tongue 

 which is bent gradually toward the remaining valve at 

 a right angle ; the tongue fills up the indentation of the 

 anterior margin of the ventral (? dorsal) valve. Un- 

 fortunately this part of the anterior margin is quite 

 damaged, so that the exact outline can no longer be 

 ascertained. The outer shell layer is preserved in a 

 few places only, and shows a very fine, concentric 

 ornamentation. Both valves are distinguished by the 

 possession of a very large, strong, median septum which 

 extends from the beak to half the length of the shell. 

 Aside from these septa, which are clearly visible on the 

 outer surface of the shell, nothing is known of the 

 interior. 



Discussion. — Gagel thought Branconia was a rhyn- 

 chonellid but found that it agreed with no known 



