CAMBRIAN BRACHIOPODA — WALCOTT 7/ 



DICELLOMUS PROLIFICUS, new species 



Plate 8, Figures 3 and sa 



This species differs from Dkcllonuts politus (Hall) [1861, p. 24], 

 to which it appears to be most nearly related, by the greater con- 

 vexity of the ventral valve, its higher umbo, and, in most shells, a 

 greater narrowing toward the apex. The dorsal valve differs from 

 that of D. politus in being more rounded on the cardinal margins. 

 It is also to be noted that no traces of muscle scars or vascular mark- 

 ings have been observed on many interiors and casts of the interior 

 of the valves, while in D. politus they are prominent on most casts 

 and often on the interior of the valves. The range of outline of the 

 valves of D. politus might include those of D. prolificns, but the con- 

 vexity of the ventral valve and the smooth interior seem to dis- 

 tinguish the latter species. 



Great numbers of the separated valves occur in several thin layers 

 of gray limestone near the summit of the cliffs on the south side of 

 Alarjum Pass. 



Formation and Locality. — ]\Iiddle Cambrian: 2,900 feet (883.9 

 m.) above the top of the Lower Cambrian and 1,500 feet (457.2 m.) 

 below the L^pper Cambrian, in gray, thin-bedded limestone of the 

 Alarjum formation [Walcott, 19080, p. 10], south side of Alarjum 

 Pass, in cliff southeast of the divide. House Range, Millard County, 

 L'tah. 



Genus BOTSFORDIA Matthew [1891, p. 148] 

 BOTSFORDIA ? BARRANDEI, new species 



Brachiopode, nouv. gen., de Verneuii, and Barrande, i860, Bull. Soc. 

 Geol. France, 2d ser., XVII, pp. 536-537, pi. viii, figs. 5, Sa-t*. (De- 

 scribed and discussed in French as a new genus.) 



Acrothclc PoMPECKj [not Linnarsson], 1896, Jahrb. kais.-konig. geol. 

 Reichsanstalt, Bd. XLV, Heft 3, p. 603. (Discussed in German; see 

 below for translation.) 



Of this species Dr. Pompeckj [1896, p. 603] writes: 



"From Barrande's description and figure, it is not quite easy to 

 interpret this species. I have before me several specimens of a 

 brachiopod from Coulouma, in the Department of Herault, which 

 Miquel [1893, p. 4] mentioned as 'la Discina.' I regard this form 

 from southern France as belonging to the genus Acrothelc, and be- 

 lieve that it is probably identical with the species mentioned by 

 de A'erneuil, Barrande, and Barrois as occurring in Spain." 



\\'ith the specimens collected by ]\L ]\Iiquel before me, and which 

 I have named Acrothcle hcrgcroni (see p. 83)', I do not think we 



