630 



CAMBRIAN BRACHIOPODA. 



shell growth m old shells. Between the large cardinal scars and the outer margin there is a 

 narrow, elongate, depressed area in which the outside and middle lateral muscles may have been 

 attached. 



Shell substance corneous. The shell is built up of numerous thin layers or lamellae, and 

 the thick growth of the old shells is by irregular accretions. The average size of the shells is 

 5 to 7 mm. in diameter. 



Observations. — This interesting form was evidently in its younger stages a siphonate shell 

 that had its pedicle tube closed by shell growth in the adult stage. I have broken several 

 ventral valves on the line of the pedicle cleft and found that the shell within the cleft has a 

 vesicular structure and that the opening could not be traced through the shell. The filing 

 up of the pedicle tube and the deposition of shelly matter about the interior opening of the 

 tube appear to have been a phase of adult growth and old age. The jBlling of the tube must 

 have cut off the pedicle and left the shell to drift about very much as in the case of Leptserm 

 rhomboidalis and Rhynchotrema capax [HaU and Clarke, 1894, p. 184]. 



This species differs from Orhicula reversa de Verneuil [1845, p. 289] in having the apex of 

 the ventral valve much nearer the posterior margin. 



Formation and locality. — TTpper Cambrian: (395) 06o^ms sandstone at Joa, near Jegelecht, 12 miles (19.3 km.) 

 east of Reval, Government of Esthonia; (395b) Obolus sandstone at Ilgast, Government of Esthonia; (9d) Oholus 

 sandstone at Jaggowal, about 20 miles (32.2 km.) east-southeast of Reval, Government of Esthonia; (336n [de Verneuil, 

 1845, p. 289]) on Ijora (Ischora) River, Government of St. Petersburg; (336o) Ungulite grit, Koporje, Government of St. 

 Petersburg; (336a [Eichwald, 1860, p. 914]) Obolus sandstone at Podolova (Putalova?) on Ijora (Ischora) River, 

 Government of St. Petersburg; and (336p) Ungulite grit, Kunitz, Government of Pskow; all in Russia. 



Superfamily ACROTRETACEA Schuchert. 



Family ACROTRETID^ Scliucliert. 

 SuMamlly ACROTHELIN.^ Walcott and Scliiicliert. 



Genus ACROTHELE Linnarsson. a 



[Bxpoc, at the top; and dri^, nipple.] 



Acrothele Linnaesson, 1876, Bihang till K. svensk. Vet.-Akad. Handl., Bd. 3, No. 12, pp. 20-21. (Described and 



discussed in English as a new genus.) 

 Acrothele Linnarsson, Zittel, 1880, Handbuch der Palseontologie, Bd. 1, Abth. 1, p. 665. (Described in German.) 



a The synonymy for this genus does not give a complete record of the various genera under which the species now included in Acrolhele were 

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

 references are listed: 



Discina (Orbicula) de Verneuil and Barrande 11860, 



p. 632]. 

 Oboldla Billings [lS62d, p. 68; 1863, p. 230). 

 OboleUa Chapman ]1863, p. 191; 1864, p. 163). 

 Oboldla Salter [1866, p. 28.5]. 

 Oboldla Davidson [1868, p. 311]. 

 Lingula Hartt [1868, p. 644]. 

 Oboldla Davidson [1871, p. 341). 

 Oboldla Ford [1873, p. 213). 

 Acrotreta ? White [1874, p. 6; 1877, p. 34). 

 AcTotkde Brogger [1878, p. 76]. 

 Lingula Hartt [1878, p. 644). 

 Acrolhde Linnarsson [1879, p. 25). 

 Obolus? Barrande ri879b, PI. CH: vn). 

 Acrothele White [1880, p. 41). 

 Discina {Acrotreta f) Brogger [1882, p. 47). 

 .<lcroftcie? Walcott [1884b, p. 14). 

 Acrothele Walcott [1884b, p. 15). 

 Billingsia Ford [1886a, p. 467). 

 Elkania Ford []886b, p. 325). 

 Acrothele Matthew [1880, pp. 39 and 41). 

 Acrotreta Walcott [1886b, pp. 107, 108, and 109). 

 Oboldla f Walcott [1886b. p. 111]. 

 Oboldla Walcott [18S6b, p. 118]. 

 Acrothele Beecher [1891, PI. XVII, fig. 12). 

 Lingula Hartt [1891, p. 644). 

 Acrothdc Walcott [1891a, pp. 608 and 609). 

 Oboldla Walcott [1891a, p. 612). 



Oboldla Hall and Clarke [1892c, p. 70). 



Acrotreta Hall and Clarke [lS92c, pp. 100 and 103). 



Acrothele Moberg [1892b, p. 114). 



Discina Miqiiel [1893, p. 9; 1894a, p. 106; 1894b, p. 



10; 1895, p. 10]. 

 Acrothele Matthew [1895a, p. 128, PI. V, figs. 7a-h, 



andPl. V.flgs. 8a-b]. 

 Acrothele Pompeokj [1896b, pp. 509-511 and 603). 

 Acrothele Matthew [1897, p. 168). 

 Linnarssonia Schuchert [1897, p. 262). 

 Acrothdc Walcott [1897b, p. 716; 1898b, p. 402]. 

 Oboldla Hobbs [1899, p. 114]. 

 Acrothele Matthew [1899b, p. 202). 

 Acrothele Grabau [1900, p. 615). 

 Linnarssonia ? Walcott [1901, p. 673). 

 Acrothele Gronwall [1902, pp. 39 and 40]. 

 Acrothele Matthew [1902b, pp. 396, 397, 398, 400, and 



402; 1902c, p. 110). 

 Acrothdc Walcott [1902, p. .598). 

 OboldU Delgado [1904, p. 364). 

 Acrothele Delgado [1904, p. 365]. 

 Acrolhde f Walcott [1905a, p. 303]. 

 Acrothele Walcott (1905b, p. 11). 

 Acrothele Moberg and Segerberg [1906, p. 67]. 

 Acrothele Shimer [1907, pp. 176 and 177). 

 Oboldla Grabau and Shimer [1907, p. 189). 

 Acrothele Walcott [1908d, pp. 82-881. 



