SYNTROPHIID^. 805 



of the same type as that of the ventral valve of SyntrojjJiia primordialis (Whitfield) (PI. CII, 

 figs. 2, 2a-b) and S. barahuensis (Winchell) (PI. CII, figs. 1, la-d). The elongate, rounded 

 form and scarcely perceptible median sinus serve to distinguish this species from all described 

 forms. 



This is the oldest shell of this tj^pe known to me. It occurs 5,525 feet below the summit 

 of the Cambrian, in the House Range section. I am not fully satisfied with the generic refer- 

 ence, but with the data available it can not well be referred to Billingsella 

 or any other known genus of the Cambrian Brachiopoda. 



Formation and locality. — 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 limestones 

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

 lope Springs, in ridge east of A^Tieeler Amphitheater, House Range [Walcott, 1908f, Pis. 

 XIII and XV], Millard County, Utah. 



Genus HTJENELLA Walcott. a 



FiGUHE 74. — Syntrophia? unxia 

 Walcott. Ventral valve, 



Syntrophia Walcott (in part) [not Hall and Clarke], 1905, Proc. U. S. Nat. Mus., vol. 28, which'The ^diTiThas been 



pp. 288-289. (Described and discussed essentially as on p. 798 (under Syntrophia), entirely removed byweatli- 



but some of the species included in the genus are now referred to Huenella.) w'^^o^' f ' ?^'' '^"^' ^■^*' 



Huenella Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 3, p. 109. (Characterized Sx, in the Middle Cambria/ 



and discussed as below as a new genus.) House Range, Utah. Copied 



Huenella Walcott, 1908, idem, No. 4, PL XI, and pp. 142 and 148. (Classification of from^Waloottii90Sd,Pl.x, 

 genus.) 



fig. 10]. 



This genus is proposed to include the more or less plicate species of the Syntrophiidae that 

 have heretofore been referred by me to the genus SyntrojjJiia. They differ from SyntropAia 

 in having a more or less radially plicate surface and sessile or pseudospondylia instead of free 

 spondylia supported by a median septum. With the exception of Huenella vermontana and 

 possibly H. etheridgei, all of the species are from the Upper Cambrian. 



The shell structure is fibrous, with many minute pores. 



Tyjje. — Syntrophia texana Walcott [1905a, p. 294]. 



The generic name is given in recognition of the thorough and valuable work of Dr. Fr. von 

 Hoyningen-Huene on the "Silurischen Craniaden." 



^. Huenella abnoemis (Walcott). 



Text figure 13, page 299; Plate CIII, figures 2, 2a-m. 



Not Camerella calcifera Billings, 1861, Canadian Naturalist, 1st ser., vol. 6, No. 4, p. 318. (Referred in this mono- 

 graph to Syntrophia calcifera.) 



Camerella calcifera Meek [not Billings], 1873, Sixth Ann. Rept. U. S. Geol. and Geog. Survey Terr, (for 1872), p. 

 464 and footnote. (Characterized.) 



Syntrophia abnormis Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, pp. 289-290. (Described and discussed as below 

 as a new species.) 



The general form varies from transverse (PI. CIII, fig. 2) to elongate (fig. 2c). Valves 

 biconvex, with dorsal very convex in some specimens. Hinge line straight. Surface marked 

 by concentric striae and imbricating lines of growth crossed by fine, rounded, radiating striae 

 and a variable number of rounded ribs; specimens occur with four ribs in the sinus of the 

 ventral valve and four on each slope outside the sinus; in other ventral valves only a trace 

 of ribs can be seen; among the specimens of the dorsal valve there are shells without a sign 

 of ribs, figure 2d, and others having from a trace of ribs on the median fold to three ribs on the 

 fold and traces on the lateral slopes. The largest shell has a length of 7 mm. ; width, 9 mm. 

 There is great variation in the proportion of the length to the width, as shown by the figures 

 illustrating the species. 



a Prior to the definition of the genus Huendla the species now referred to that genus were described under the following genera: 

 Camerella Shumard [1861, p. 221]. I Orthis or Ortlusina Etheridge [1905, p. 250]. 



Camerella Meek [1873, p. 464). | SyntropUa Walcott [1905a, p. 288]. 



