450 



CAMBRIAN BRACHIOPODA. 



This position of the traces of the area, which is far removed from the peduncular groove, appears to point to the 

 relative size of the embryonal shells — a conjectui'e to which the consideration of the broad, parallel-bordered peduncular 

 groove of 0. obtusus has already led. In the small shell, the traces of the pseudo-area run exactly in the same man- 

 ner, and inclose the flatly deepened splanchnocoelic part of the area between them, which allows a shallow, rather 

 broad groove in the median line, opposite the peduncular groove of the large shell, to be perceptible by reflected 

 light. 



The thickening of the shells is generally very slight, and therefore the configuration of the inner surface stands 

 out but little. Nevertheless, predominant fluctuations occur also in this species. It is noteworthy that of all the 

 formations which stand out from the sm'face of the shell, the median swelling of the small shell is the most given 

 to variations, which often degenerate in a monstrous manner. * * * Xhe heart-shaped groove is given to 

 similar alterations of form as we have learned in 0. celatus, and may be partly dependent on the strength of the 

 thickening * * *. 



The places of attachment of the muscles are in general distinctly pronounced, but not so sharply bordered as with 

 the large forms of Eichwald's genus. Especially there are here also, as with 0. celatus, the large central spots of attach- 

 ment of the large shell, only with difficulty decomposable into their constituent parts. As with the previous species, 

 the outside lateral muscles are delimited from the central muscles and form, close to the principal vascular canals, 

 isolated, shallow-pitted, excavated places of attachment. 



Of the principal vascular canals there can be distinguished on all the specimens at hand, in both shells, only the 

 posterior parts; in the small shells, besides, as a rule, also the ends, curved around posteriorly and du-ected toward the 

 places of attachment of the anterior lateral muscles. The first are very broad, flat, and divided by a median swelling, 

 which often appears to be a prolongation of the lateral septa. The latter in no way deviates from the usual arrange- 

 ment. Of the accessory vascular' canals there can be observed only slight indications of the inwardly radiating canals, 

 which show as somewhat lighter colored lines. 



Formation and locality." — ^Tipper Cambrian: Obolus sandstone at the following localities: (395) At Joa, near 

 Jegelecht, 13 miles {19.3 km.) east of Reval; and (395b) at Ilgast; both [Mickwitz, 1896, p. 171] in the Government 

 of Esthonia, Russia. 



(321c [Wiman, 1902, p. 68]) Drift bowlder of Obolus sandstone. No. 17, on Fanton Island, parish of Borstil, 

 Province of Stockholm, Sweden. 



WESTONIA Walcott,6 subgenus of OBOLTJS. 



Obolus ( Westonia) Walcott, 1901, Proc. U. S. Nat. Mus., vol. 23, pp. 683 and 691. (Described on latter page, as below, 



as a new subgenus.) 

 {Westonia) Walcott, Matthew, 1903, Geol. Survey Canada, Kept. Cambrian Rocks Cape Breton, pp. 205-206. (Copies 



original description, and discusses the form as a subgenus more allied to Lingulella than Obolus.) 

 Lingulella Grabau and Shimer [not Salter], 1907, North American Index Fossils, vol. 1, p. 192. (Described as 



Lingulella, but both species that are referred to it belong with Obolus {Westonia).) 

 Obolus { Westonia) Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 4, PI. XI, and pp. 142 and 144. (Classification 



of genus.) 



Ovate, with ventral valve slightly acuminate; area of ventral valve strongly defined and 

 divided by a relatively large pedicle groove. Surface marked by concentric and radiating 

 striae that are crossed by transverse, semi-imbricating, "ripple-embossed" lines. So far as 

 known, the muscle scars and vascular marldngs are essentially the same as in Oholus. 

 Type. — Lingula aurora Hall. 



Of the species referred to Westonia, Oholus ( Westonia) aurora (Hall), 0. ( W.) ella (Hall and 

 Whitfield), 0. {W.) eughjphus (Walcott), 0. ( W.) chuarensis (Walcott), 0. ( TF.) stoneanus 



o Locality 395 is represented in the United States National Museum collections. 



b The s3^nonymy for this subgenus does not give a complete record of the various genera under which the species now included in Westonia 

 were formerly placed; it gives only those references in which the genus is discussed or described. To complete the record the following mere generic 

 references are listed; 



Lingula Hall [1861, p. 24]. 



Lingula Rogers [isei, p. 390; 1862, p. 4; 1863, pp. 



126 and 127; 1867, pp. 103 and 104]. 

 Lingulella Hall [1873, p. 244], 

 Lingulepis Hall and Whitfield [1877, p. 232]. 

 Lingula Barrande [lS79b, Pis. CVI and CXI]. 

 Lingulella Whitfield [1882, p. 344]. 

 Lingulella Walcott [1886b, p. 97; 1891a, p. 607]. 

 Lingulella Hall and Clarke [1892c, p. 58 and PI. II, 



figs. 9-11 and 12-13]. 

 Lingula Sardeson [1896, p. 95]. 

 Lingulepis Walcott |1897a, p. 404]. 

 Obolus (Lingulella) Walcott [1898b, pp. 399, 402, 



and 413, and PI. XXVIII]. 



Lingulella Grabau [1900, p. 624]. 



Lingulella ? Matthew [1901a, p. 270]. 



Lingula Wiman [1902, p. 51]. 



Lingulella? Wiman [1902, p. 52]. 



Obolus Matthew |1902c, pp. 96 and 110]. 



Obolus (Westonia) Walcott [1902, p. 611]. 



Lingulella Weller [1903, p. 112]. 



Obolus (Westonia) Walcott [1905a, pp. 334, 335, 336, 



and 337]. 

 Lingulella Pack [1906, p. 296]. 

 Lingulella (Westonia) Grabau and Shimer [1907, 



p. 193]. 

 Obolus (Westonia) Walcott [1908d, pp. 67, 68, and 69). 



