OBOLIDiE. 485 



The area of the ventral valve is elongate, being nearly one-fifth the length of the shell. It 

 is divided midway by a very distinctly defined pedicle furrow. The flexure line is just percep- 

 tible about half the distance out from the pedicle furrow to the lateral margin. 



The area extends well forward on the cardinal slopes and is marked by strong striae of 

 growth parallel to its base. The area of the dorsal valve is shorter than that of the ventral, 

 and is marked by fine lines of growth and clearly marked flexure lines that extend from the 

 apex forward on a line with the main vascular sinuses. 



The cast of the interior of the ventral valves shows a general outline of the visceral cavity 

 and the main vascular sinuses. Only the base of the main vascular sinus has been seen in the 

 dorsal valve. 



Observations. — This very pretty little species occurs in association with Paradoxides. In 

 my first study of the brachiopods collected by S. Ward Loper from Cape Breton I confused it 

 [1901, p. 694] with the young of Lingulella (Lingulepis) gregwa (Matthew). By means of a larger 

 collection made by Loper in 1901, I have been able to separate it from the young of the associ- 

 ated Lingulella (Lingulepis) exigua (Matthew) and from somewhat similar species that occur at 

 a lower horizon, Lingulella atava (Matthew) and L. collicia (Matthew). It differs from both the 

 latter species in having a more elongate oval outline. It differs from the young of Lingulella 

 (Lingulepis) gregiva in being more regularly oval and in having the posterolateral margin 

 curved uastead of nearly straight. 



Formation and locality. — Middle Cambrian: (3i) Compact, fine-grained, thin-bedded, gray sandstone of the 

 Paradoxides zone, on McLeans Brook, 1 mile {1.6 km.) east of McCodrum Brook and 1.5 miles (2.4 km.) west of Marion 

 Bridge; and (10s) sandstone on McLeans Brook, near Marion Bridge; both in eastern Cape Breton, Nova Scotia, Canada. 



Lingulella cedens (Barrande) 



Plate XXX, figure 8. 



Lingula cedens Barrande, 1868, Faune silurienne des environs de Hof, en Bavifere, p. 102, fig. 66. (Described in 



French. Fig. 66 is copied in this monograph, PL XXX, fig. 8.) 

 Lingula cedens Barrande, 1868, Neues Jahrb. t'tlr Mineralogie for 1868, jjp. 691-692, unnumbered plate, fig. 66. (Copy 



of preceding reference.) 



This is one of the larger shells of the fauna at Hof, but as it is deformed by pressure it is 

 difficult to give its specific characters. The author states that the surface of the internal cast 

 contains traces of rather strong concentric strise, with finer intermediate striae; also traces of 

 very fine longitudinal striae. Length, 18 mm.; greatest width, 12 mm. 



Barrande [1868a, p. 102] compares this form with Lingulella davisi (McCoy), from which it 

 appears to be very little different. It is probable that an extended series of specimens would 

 unite it with Lingulella wirthi (Barrande). 



Formation and locality. — Passage beds between the Upper Cambrian and the Ordovician: (303c [Barrande, 

 ISeSa, p. 102]) Suburbs of Hof ; and (303f [Pompeckj, 1896a, pp. 7 and 8]) railway cut near Schellenberg, a little dis- 

 tance back of the railway station at Neuhof, near Hof; both in Bavaria, Germany. 



Lingulella clarkei n. sp. 



Text figures 42A-D, page 486. 



The ventral valve of this species has the same general outline and form as that of Lingulella 

 acutarujula (Roemer) (PI. XVII, figs. 1, la, Ig) except that it is a little broader across the front. 

 The dorsal valve differs materially in being proportionally narrower on the posterior half and 

 in having a broad shallow sinus extending from the umbo to the front margin. A similar sinus 

 occurs on one dorsal valve of Lingulella manticula (Wliite) (PI. XX, fig. la) and on all dorsal 

 valves of Oholus (Fordinia) perfectus Walcott (PI. LXIII, fig. 10b). 



The largest ventral valve has a length of 9 mm.; width, 7 mm. A broad dorsal valve has 

 a length of 5 mm.; width, 4.25 mm. 



