660 CAMBRIAN BEACHIOPODA. 



I do not regard this variety as having much value, as there are numerous gradations from 

 the smooth surface to the granulated surface typical of the species. 



The associated fossils indicate the central portion of the Middle Cambrian section at 

 about the horizon of the lower portion of the Marjum limestone of the House Range section 

 of Utah. 



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

 quartzitic sandstones of the Cambrian, at Ophir, Oquirrh Range, Tooele County; and (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 Antelope Springs, in ridge east of Wheeler Amphi- 

 theater, House Kange [Walcott, 1908f, Pis. XIII and XV], Millard County; both in Utah. 



ACROTHELE TUENERI Walcott. 

 Plate LX, figures 7, 7a. 



Acrothele tumeri Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 3, pp. 87-88, PI. IX, fig. 12. (Described and 

 discussed as below as a new species. Fig. 12 is copied in this monograph, PL LX, fig. 7.) 



General outhne broad oval, ventral valve sUghtly conical, with the apex at about the 

 posterior third of the length of the valve; apex short and perforated on the back side of its 

 point by a minute pedicle opening; false area indicated by a sUght flattening between the 

 apex and posterior margin. Dorsal valve gently convex ; Ijeak marginal. 



Surface marked by fine concentric hnes and strise of growth. Shell corneous and made 

 up of a few very thin lamellae. 



The largest shell has a length of 2.5 mm.; width, 2.75 mm. 



Observations. — Tins neat httle shell differs from Acrothele subsidua (White) in the absence 

 of the surface characters of that species and from A. spurri by the more anterior position of 

 its beak and smooth surface. It belongs to the group of J.cro<?ieZe represented by J., horgliolm- 

 ensis. (Compare PI. LX, fig. 7, with PL LXIII,' fig. 2.) 



The specific name was given in honor of Mr. H. W. Turner. 



Formation and locality. — Middle Cambrian: (7r) Calcareous shales- 4 miles {6.4 hm.) south-southeast of Emi- 

 grant Peak, Silver Peak quadrangle ( U. 8. Geol. Survey), Esmeralda County, Nevada. 



Specimens that are somewhat doubtfully referred to Acrothele tumeri Walcott occur at the 

 following locality: 



Middle Cambrian: (54a) About 750 feet (228.6 m.) above the Brigham quartzite and 3,440 feet (1,048.5 m.) 

 below the Upper Cambrian, in the shales forming 2a of the Ute limestone [Walcott, 1908f, p. 196], in Blacksmith Fork 

 Canyon, about 10 miles (16.1 km.) east of Hyrum, Cache County, Utah. 



Acrothele villaboimensis Delgado. 



Acrothele villaboimensis Delgado, 1904, Communicafoes Commissao Servijo Geol. Portugal, tome 5, fasc. 2, p. 365, 



PL IV, fig. 28. (Described and discussed in French as a new species.) 

 Obolella mamlata Delgado [not Salter], 1904, idem, p. 364, PL IV, fig. 24. (Discussed in French.) 



Delgado [1904, p. 365] states that this species is characterized by the longitudinally oval 

 outhne of the ventral valve. The photograph of the type specimen shows that the apex is a 

 short distance from the posterior margin, and that distinct concentric lines of growth occur, 

 also that there are tliree or more fine plications near the front margin. The presence of the 

 plications appears to indicate that the specimen has been laterally compressed, and thus given 

 a longitudinally oval outhne. If this view is correct the outline of the ventral valve was prob- 

 ably nearly circular. It may be that Plate IV, figure 24, of "Obolella maculata" [Delgado, 1904, 

 p. 364] represents the dorsal valve of this species. 



The onty form with which we can compare this species is Acrothele maculata (Salter) 

 of the Mddle Cambrian of Wales. Both species have the apex of the ventral valve far back 

 toward the posterior margin. Distorted specimens of the ventral valve of Acrothele maculata 

 have the same outline as the ventral valve of A. villaboimensis. It is not probable that they 



