OBOLID^. 489 



Specimens somewhat doubtfully referred to this species occur at the following locality : 



Middle Cambrian: (167) Sandstone beneath limestone and resting on the pre-Cambrian in a bluff 9 miles (14.4 

 km.) west of Custer, Black Hills, South Dakota. 



LiNGULELLA DAMESI (Walcott)." 



Plate XXXIX, figures 8, 8a-c. 



Oholus (Lingulella) dnmesi Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, p. 329. (Characterized as below as a new 

 species.) 



The general descriptions of Oholus cMnensis (Walcott) (p. 387) and Lingulella prima (Hall) 

 (p. 526) apply so closely to this species that it does not appear necessary to do more than call 

 attention to the points in which they differ. From Oholus cMnensis (PL XXXIX) this species 

 varies in having a more elongate, acuminate ventral valve and a more ovate dorsal valve; the 

 valves are also less convex. From Lingulella prima (PI. XXVII) it differs in the more gradual 

 curvature of the sides from the apex to the front margin, in this respect resembling some varieties 

 of L. ferruginea Salter (PI. XXIX). The average size of the ventral valve is about 5 mm. in 

 length by 3.5 mm. in width. 



The specific name was given in honor of Dr. W. Dames. 



Formation and locality. — Middle Cambrian: (C7) Lower limestone member of the Kiulung group [Black- 

 welder, 1907, pp. 37 and 39 (last list of fossils), and fig. 8a (bed 33), p. 29], 2.2 miles (3.5 km.) southwest of Yenchuang; 

 and (CIO) lower shale member of the Kiulung group [Blackwelder, 1907, pp. 37 and 40 (part of 3d list of fossils), and fig. 

 8a {bed 35), p. 29], about 3 miles (4.8 hn.) southwest of Yenchuang; both in the Sintai district, Shantung, China. 



A shell which may be a variety of this species occurs at the following locahty: 



Upper Cambrian: (C64) Upper limestone member of the Kiulung group [Blackwelder, 1907, pp. 37 and 42 (first 

 list of fossils), and fig. 10 (bed 20), p. 38], 2.7 miles (4.3 km.) southwest of Yenchuang, Sintai district, Shantung, 

 China. 



Lingulella davidsoni (Barrande). 



Plate XXXII, figures 1, la-e. 



Lingula davidsoni Barrande, 1879, SystSme silurien du centre de la Boheme, vol. 5, PL CIV, figs, vixi: 1-4. (Not 

 described, but figured as a new species. PL CIV, figs, viii: lA, lb, 3A, 3b, 4E, and 4 are reproduced in this 

 monograph, PL XXXII, figs. 1, la-e, respectively.) 



In the absence of specimens for study an opinion of the generic relations of this fine species 

 is necessarily based on the illustrations given by Barrande. Comparing Plate XXXII, figures 

 1 and lb, with Plate XVII, figure la, we note at once the similarity between Lingulella davidsoni 

 and L. acutangula (Roemer) in their general form and the character of their areas as far as shown 

 for Lingulella davidsoni. Fragments of the exterior shell of the latter (PI. XXXII, fig. lb) 

 may be compared with the exterior surface of the former (PL XVII, fig. 1). The dark oval 

 spots in front of the area in figure Id may be of importance, or they may represent only a depres- 

 sion on each side of the median ridge such as often occurs in compressed shells. If this species 

 is a typical Lingulella, it is one of the last of its race, occurring as it does in Etage d4 of 

 Barrande's section. 



The specific name was given in honor of Thos. Davidson. 



Formation and locality. — Ordovician: (303m) Etage d4 at Lieben; (303n) Etage d4 at Wraz; and (303o) 

 Etage d4 at Lodenitz; all [Barrande, 1879b, PL CIV] in Bohemia, Austria-Hungary. 



Lingulella davisi (McCoy). 



Plate XXX, figures 2, 2a; Plate XXXI, figm-es 6, 6a-h. 



Lingula sp. Davis, 1846, Quart. Jour. Geol. Soc. London, vol. 2, pt. 1, p. 70. (Mentioned only.) 

 Not Lingula ovata McCoy, 1846, Silurian Fossils of Ireland, p. 24, PL III, fig. 1. (Described and discussed. This 

 species is not taken up in this monograph.) 



a Better preserved and more complete series of specimens of tliis species collected by i)r. J. P. Iddings, in Manchuria, indicate that the form 

 bears a closer relationship to Obolus than to Lingulella. In the volume on Paleontology of Willis's work on Eesearch in China (Carnegie Insti- 

 tution of Washington) the species will be described and figured under the title, Obolus iamesi (Walcott). 



