PATERINIDiE. . 365 



^ MicROMiTRA (Iphidella) pannula ophieensis (Walcott). 

 Plate IV, figures 4, 4a-f . 

 Iphidella pannula ophircnsis Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, p. 306. (Characterized as" a new variety.) 



Surface formed by raised, concentric lines and ridges tliat inosculate and become more and 

 more irregular until the tj^pical surface of Micromitra (IpJiidella) pannula is developed. 

 This form owes its varietal name to its occurrence at Ophir, Utah. 

 Formation and locality. — Middle Cambrian: (3e) Thin-,bedded limestones less than 400 feet (121.9 m.) above the 

 quartzitic sandstones of the Cambrian, near Ophh-, Oquirrh Range, Tooele County, Utah. 



Shells that I can not separate from this variety occur at the following localities: 



Middle Cambrian: (3x) About 2,200 feet (670.6 m.) above the Lower Cambrian and 2,200 feet (670.6 m.) below the 

 Upper Cambrian, in the limestone forming Id of the Marjum limestone [Walcott, 1908f, p. 180], 2.5 miles (4 km.) east of 

 Antelope Springs, in ridge east of Wheeler Amphitheater; and (llo) about 2,750 feet (838.2 m.) above the Lower Cam- 

 brian and 1,650 feet (502.9 m.) below the Upper Cambrian, in limestone at the base of la of the Marjum lime- 

 stone [Walcott, 1908f, p. 179], about 4 miles (0.4 km.) southeast of Antelope Springs, in the spur at the junction of the 

 Deseret and Swasey Spring roads; both in the House Range fWalcott, 1908f, PL XIII], Millard County, Utah. 



(54s) Dark blue-gray Langston limestone [Walcott, 19081, p. 198], just above the Cambrian quartzitic sandstones, 

 on the north side of Twomile Canyon, near its mouth, 2 miles (3.2 km.) southeast of Malade, Oneida County, Idaho. 



(14s) About 2,300 feet (701 m.) above the Lower Cambrian and 2,700 feet (823 m.) below the Upper Cambrian, in 

 the Ogygopsis zone of the Stephen formation [Walcott, 1908f, p. 210], northwest slope of Mount Stephen, above Field 

 on the Canadian Pacific Railway, British Columbia, Canada. 



Fragments of shells that are not to be separated by their surface characters from Micro- 

 mitra {Iphidella) pannula opMrensis occur in China. The fragments also indicate that the 

 shells were about the same size and form. 



Middle Cambrian: (C5) Lower limestone member of the Kiulung group [Blackwelder, 1907a, pp. 37 and 39], 3.2 

 miles (5.1 km.) southwest of Yenchuang, Sintai district. Shantung, China. 



Genus VOLBOK.THIA von Moller.o 



Volhorihia von Moller, 1874, Neues Jahrb. fur Mineralogie, pp. 449^52. (Described and discussed in German as a 

 new genus; see below for free translation of description on pp. 449^51.) 



AcTotreta {Volborthia) {won Moller), Oehleet, 1887, Manuel de conchyliologie, by Fischer, p. 1266. (Described in 

 French as a subgenus, with figures of "Acrotreta ( Volhorthia) reeurva (Kutorga).") 



Volborthia von Moller, Hall and Clarke, 1892, Eleventh Ann. Rept. State Geologist New York for 1891, p. 249. 

 (Described.) 



Volborthia von Moller, Hall and Clarke, 1892, Forty-fifth Ann. Rept. New York State Mus. for 1891, p. 565. (Copy 

 of preceding reference.) 



Volborthia von Moller, Hall and Clarke, 1892, Nat. Hist. New York, Paleontology, vol. 8, pt. 1, pp. 95-96. (Original 

 description, von Moller, 1874, pp. 449^51, translated essentially as below and genus discussed.) 



Volborthia von Moller, Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 4, PL XI, and pp. 142 and 143. (Classifi- 

 cation of genus.) 



The description in substance by von Moller [1874, pp. 449-451] is as follows: 



The shells remind one in their form of a broad horn whose opening is closed through a very convex cover (the 

 dorsal valve). Seen from above, the outline of the figured shell, in consequence of the rounded edges and the likewise 

 rounded front edge, is transversely oval. Only the posterior edge, whose length is about one-half of the breadth of the 

 shell, appears straight. 



The ventral valve is very high, conical, and has a strong, recurved, prominent beak without any perforation. 

 Between the beak and the hinge line (posterior edge) is a distinctly marked and high three-cornered area, whose length 

 is divided by a narrow ridge extending from the beak to the middle of the straight hinge line. 



The dorsal valve is convex, nevertheless decidedly lower than the ventral, and it has just such a beak as the other. 

 Although this beak lies in the same vertical line with that of the opposite valve, it nevertheless touches the hinge line 

 of the shell, without any area lying between. 



The surface of both valves is smooth and covered only with very fine concentric growth strise, which extend 

 without interruption also over the area of the ventral valve. On the latter they appear much coarser and not so 

 regular, especially on the ridge where these strise are rather strongly bent downward toward the beak of the ventral 

 valve. 



Neither the ventral nor the dorsal valves appear to have inward projections; at least the casts (molds) show not the 

 slightest traces thereof. Likewise the muscle scars are not known, and on the casts are usually found only a small 



"■ Prior to the definition of Volborttiia by Ton Moller [1S74, p. 449] tlie species now referred to this genus was placed under Acrotreta Kutorga 

 [1848, p. 277]. 



