ACROTRETID^. 703 



Oholella sabrinx (Callaway), Davidson, 1883, British Fossil Brachiopoda, vol. 5, pt. 2, p. 211, PI. XVI, figs. 27, 27a, 

 27d, 28, and 28a. (Described and discussed.) 



Oholella? scabrinse (Callaway), Walcott, 1884, Mon. U. S. Geol. Survey, vol. 8, PI. I, fig. Ic. (Not described, and 

 figure copied from Davidson, 1883, PI. XVI, fig. 27d.) 



Obolella sabrinse (Callaway), Hall and Clarke, 1892, Nat. Hist. New York, Paleontology, vol. 8, pt. 1, p. 103, fig. 

 58. (Mentioned in the text and figure copied from Davidson, 1883, PI. XVI, fig. 27d.) 



Acrotreta sp. cf. nicholsoni Davidson, Matley, 1902, Quart. Jour. Geol. Soc. London, vol. 58, pt. 1, p. 142, fig. 10. 

 (Discussed in text as Acrotreta sp., and figured as A. sp. cf. nicholsoni.) 



Acrotreta {?) sabrinx (Callaway), Matley, 1902, idem, p. 143. .(Discussed.) 



Acrotreta {?) sabrinx malvernensis Matley, 1902, idem, pp. 143-144, figs. 11-14. (Described and discussed as a new 

 variety.) 



Acrotreta sp. cf. A. socialis von Seebach, Matley, 1902, idem, pp. 144-145, figs. 15 and 16. (Characterized and dis- 

 cussed.) 



As in the case of most species of Acrotreta preserved in shales, the ventral valves of this 

 form are so compressed as to prevent our getting the true elevation. With several fairly well- 

 preserved specimens to judge from I think the height was about two-thirds of the greatest diam- 

 eter of the shell. A ' partial cast of the interior shows a small apical callosity and the base 

 of the cast of a small pedicle tube. The interior of the dorsal valve is almost bisected by a 

 strong median ridge; the cardinal scars are also prominent. 



A fragment of the outer shell shows fine, concentric striae and lines of growth that are 

 fretted by very fine undulating striae. 



Through the courtesy of Dr. Charles Lapworth I have had the opportunity of studying and 

 illustrating the type specimen of Callaway's ''Oholella sahrinse" (PL LXXIII, fig. 5b). It is 

 a cast of the dorsal valve preserving little more than the impression of the strong median ridge 

 and a trace of the area. Dr. Lapworth also sent me several other specimens of this species; 

 these are illustrated on Plate LXXIII, figures 5, 5a, 5c, and 5d. Davidson [1883, PI. XVI, 

 fig. 27d] illustrates an interior of a dorsal valve in which the median ridge and the cardinal 

 and central scars are clearly defined. He also gives [1883, PI. XVI, figs. 27, 27a] the exterior 

 of a compressed ventral valve and a side view of the two valves united. 



Of described species, Acrotreta hisecta Matthew approaches tliis most closelj''. It is quite 

 probable that with a good series of specimens of each species for comparison the two forms 

 would be referred to the one species of Callaway. 



Matley [1902, p. 143, figs. 11-14] illustrates and describes some crushed specimens from 

 the lowest black shales of the Malvern Hills, which he tentatively gives the value of a variety 

 of this species under the name malvernensis. With examples from the typical locahty before 

 me for comparison with the pi'oposed variety, I am inchned to consider the latter of such 

 doubtful value as to leave it out of this work. 



He also [Matley, 1902, p. 144] mentions an Acrotreta as sp. cf. A. socialis von Seebach 

 from a higher stratigraphic horizon. Acrotreta socialis as now restricted is confined to the 

 Middle Cambrian. I do not think that the material as illustrated and described by Matley 

 clearly indicates a form distinct from Acrotreta sahrinse, if allowance is made for the crushed 

 condition of most specimens of the latter species. The shell mentioned as Acrotreta sp. cf. 

 nicholsoni [Matley, 1902, p. 142] may also be a large specimen of this species. 



The shells figured by Matley [1902, p. 141, figs. 7 and 8] as Lingulella (?) sp. and [1902, 

 p. 142, fig. 10] as Lingula (?) sp. I think are either Acrotreta or Acrothyra, probably the latter. 



Formation and locality.« — Upper Cambrian : (304h and 3041 [Callaway, 1877, p. 669]) Shineton shale, at Shineton, 

 Mary Dingle, Dryton, Cressage, 1 mile {1.6 km.) west of Cressage, west of Harley, and under Cound-Moor quarry, all in 

 South Shropshire, England. 



(304p) Shineton shales at the following localities of the Geological Survey of Great Britain: 2495, 2536, 2543, 

 2545, 2558, and 2580, all of which are on Shineton Brook, South Shropshire, England. 



(304j) Lower Stockingford shales, Puxley Park lane, halfway up the path to the quarry, Atherstone, Warwick- 

 shire; (304a [Groom, 1902, p. 110]) "Bronsil" shales, Malvern Hills; and (304b [Groom, 1902, p. 109]) lower part of 

 the "White Leaved Oak" shales (the zone of Polyphyma), Malvern Hills; all in England. 



a Localities 304h and 304j are tlie only localities represented in the United States National Museum collections. 3041i is the type locality. 



