SIPHONOTRETIDiE. 625 



Siphonotreta de Verneuil, Morris, 1850, Rept. British Assoc. Adv. Sci. for 1849, Notices and Abstracts, pp. 57-58. 



(Notes on the genus.) 

 Siphonotreta de Vemeuil, Davidson, 1853, British Fossil Brachiopoda, vol. 1, Introduction, No. 3, pp. 131-133. 



(Described and discussed.) 

 Siphonotreta de Verneuil, Eichwald, 1860, Letheea rossica, ancienne periode, vol. 1, sec. 2, p. 915. (Described in 



French.) 

 Siphonotreta de Vemeuil, Seebach, 1865, Zeitschr. Deutsch. geol. Gesell. for 1865, Bd. 17, Heft. 2, p. 341. (Discussed 



in German.) 

 Siphonotreta de Vemeuil, Davidson, 1866, British Fossil Brachiopoda, vol. 3, pt. 7, No. 1, p. 75. (Mentioned.) 

 Siphonotreta de Vemeuil, Qtjenstedt (in part), 1871, Petrefactenkunde Deutschlands, Abth. 1, Bd. 2, Brachiopoden, 



pp. 673-674. (Described and discussed in German.) 

 Siphonotreta de Verneuil, Davidson, 1877, Geol. Mag., new ser., dec. 2, vol. 4, pp. 13-16. (Notes on the genus and 



its generic relations.) 

 Siphonotreta de Verneuil, Zittel, 1880, Handbuch der Palseontologie, Bd. 1, Abth. 1, pp. 665-666. (Described in 



German.) 

 Siphonotreta de Verneuil, Davidson, 1883, British Fossil Brachiopoda, vol. 5, pt. 2, pp. 217-219. (Discussed.) 

 Siphonotreta de Verneuil, Oehlbrt, 1887, Manuel de conchyliologie, by Fischer, p. 1265. (Described in French, 



with figures of S. unguiculata and S. verrucosa.) 

 Siphonotreta de Vemeuil, Hall and Clarke, 1892, Eleventh Ann. Rept. State Geologist New York for 1891, pp. 



252-253. (Described.) 

 Siphonotreta de Verneuil, Hall and Clarke, 1892, Forty-fifth Ann. Rept. New York State Museum for 1891, pp. 568-569. 



(Text copied from preceding reference.) 

 Siphonotreta de Verneuil, Hall and Clarke, 1892, Nat. Hist. New York, Paleontology, vol. 8, pt. 1, pp. 110-113. 



(Described and discussed.) 

 Siphonotreta de Verneuil, Winchell and Schuoheet, 1895, Nat. Hist. Minnesota, Geology, vol. 3, pt. 1, Paleontology, 



p. 358. (Copies the description given by Hall and Clarke, 1892c, pp. 110-111.) 

 Siphonotreta de Verneuil, Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 4, PL XI, and pp. 142 and 146. (Clas- 

 sification of genus.) 



For the diagnosis of the genus, see Hall and Clarke [1892c, pp. 110-113]. 



The following notes are the result of the study of casts of a natural mold of the interior 

 of the two valves united that I worked out from a specimen of S. unguiculata (PL LXXXI, 

 figs. 6, 6a-b) received from Dr. Fr. Schmidt, in which the transverse diameter is 18 mm. 



The cast of the interior of the ventral valve shows that the visceral area was elevated 

 on a thickening of the shell, and that the muscle scars were attached in depressions in front 

 of and beside the elevated visceral area; the main vascular canal was also on a ridge where it 

 passed from the anterolateral edge of the visceral area. The points of attachment of the 

 central, outside lateral, and middle lateral scars are not clearly defined as distinct scars in the 

 specimens at hand, but the space occupied by them is very distmctly marked. It is very much 

 like that of Obolus afoUinis Eichwald (PI. VII). The points of attachment of the transmedian 

 and anterior lateral muscles are close to the elevated visceral area, just outside of the ridge 

 beneath the main vascular sinuses. The opening of the pedicle tube is not well preserved; 

 this feature is illustrated by Davidson [1877, PI. II, figs. 8 and 9]. 



The interior of the dorsal valve shows a thickening of the shell in front of the antero- 

 lateral muscle scars so as to form a transverse ridge that unites with the median ridge and a 

 ridge on each side that appears to have been beneath the mam vascular canals; within the 

 subtriangular space thus formed the rather large anterolateral muscle scars occur as pits, 

 and a little back of them, and of about the same size, the elongate oval central muscle scars; 

 outside of the lateral ridge occur three large oval scars that correspond in position to the trans- 

 median, outside lateral, and middle lateral scars of the dorsal valve of Oholus. 



The specimens studied by Davidson illustrate the interior of the ventral valve somewhat 

 better than those before me, but the interior of the dorsal valve does not appear to have been 

 so good. 



Type. — Crania unguiculata Eichwald. 



Siphonotreta ? dubia n. sp. 

 Plate LXXXI, figures 7, 7a-b. 

 Shell small, subcircular in outline. Ventral valve subcorneal, with the apex a short dis- 

 tance in front of the posterior margin and directed backward; it is truncated by a small, round 

 62667°— VOL 51, pt 1—12 40 



