OBOLID^. 437 



ACBITIS Volborth,a subgenus of OBOLTTS. 



[Ikpiwc, indiscernible.] 



Aulonotreta Kutorga (in part), 1848, Verhandl. Russ.-kais. min, Gesell. St. Petersburg for 1847, No. 12, pp. 278-279. 

 (Described and discussed in German as a new genus. The species referred to the genus belong with Obolus, 

 Obolus (Acritis), and Obolus (Mickwitzella).) 



Aulonolreia Kutorga, Morris, 1849, Annals and Mag. Nat. Hist., 2d ser., vol. 4, pp. 316-317. (Characterized and 

 discussed as a synonym of Obolus.) 



OboliLS Eichwald, Davidson (in part), 1853, British Fossil Brachiopoda, vol. 1, introduction. No. 3, pp. 135-136. 

 (Described and discussed. As far as they have been identified in this monograph the species referred to the 

 genus belong with Obolus, Obolus (Acritis), and Obolus {Miclnvitzella).) 



Obolus Eichwald (in part), 1860, Lethsea rossica, ancienne periode, vol. 1, sec. 2, pp. 924-925. (Described in French. 

 The species referred to the genus belong with Obolus, Obolus {Acritis), and Obolus {Mickwitzella) .) 



Acritis Volborth, 1869, Verhandl. Russ.-kais. min. Gesell. St. Petersburg, 2d ser., Bd. 4, pp. 212-217. (The descrip- 

 tion and discussion of the genus (in German) is incorporated with that of Obolus {Acritis) anliquissimus.) 



Acritis Volborth, Dall, 1877, Bull. U. S. Nat. Mus. No. 8, p. 11. (Placed as a synonym of Aulonotreta.) 



Aulonotreta Kutorgn, Dall, 1877, idem, p. 16. (Priority of this generic name over ,4OT<?sdiscussed.) 



Acritis Volborth, Oehlert, 1887, Manuel de conchyliologie, by Fischer, p. 1264. (Described in French.) 



Aulonotreta Kutorga, Hall and Clarke (in part), 1892, Eleventh Ann. Kept. State Geologist New York for 1891, pp. 

 243-244, (Described and discussed. As discussed the genus include's species referred to both Obolus and 

 Obolus {Acritis).) 



Aulonotreta Kutorga, Hall and Clarke (in part), 1892, Forty-fifth Ann. Rept. New York State Museum for 1891, 

 pp. 559-560. (Copy of preceding reference.) 



Aulonotreta Kutorga, Hall and Clarke (in part), 1892, Nat. Hist. New York, Paleontology, vol. 8, pt. 1, p. 82. (De- 

 scribed and discussed and priority, etc., of generic references discussed. As discussed, the genus includes 

 species referred to both Obolus and Obolus {Acritis).) 



Obolus (Acritis) (Volborth), Mickwitz, 1896, M^m. Acad. imp. sci. St.-P6tersbourg, 8th ser., vol. 4, No. 2, pp. 205-206. 

 (Characterized and discussed in German as a subgenus; see below for translation.) 



Obolus (Acritis) (Volborth), Walcott, 1901, Proc. U. S. Nat. Mus., vol. 23, p. 683. (Characterized.) 



Obolus (Acritis) Volborth, Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 4, PI. XI, and pp. 142 and 144. (Classi- 

 fication of subgenus.) 



Mickwitz describes the subgenus as follows : 



The subgenus Acritis, like the two preceding subgenera, Thysnnotos (^Micku'itzelhi) and Lepteinbolon, is based on 

 a single species, Obolus anliquissimus Eichwald, which, out of all the species of Eichwald's genus, departs most widely 

 from the typical species. 



The most prominent characteristics of this subgenus — apart from the parallelism of the concentric striation of the 

 surface of the shell, which it has in common with the subgenus Thysanotos {= Midcu'itzella) — consist in the remarkable 

 shortening of the splanchnocoele, which even in the adult stage of the animal advances but little toward the frontal 

 edge, and in the different arrangement of the deposit of the thickened lamellae, which impart to the adult shells a 

 totally different appearance. 



The failure to recognize these facts was the main cause of the long controversy over the genus of O. anliquissimus, 

 which after all threw no light on the subject. 



Type. — Oholus (Lucina) antiquissimus Eichwald [1843, p. 142]. 



Obolus (Acritis) antiquissimus (Eichwald). 

 Plate XIII, figure 3; Plate XV, figures 2, 2a-d. 



Obolus (Lucina) antiquissimus Eichwald, 1843, Beitrage zur Kenntniss des russischen Reiches, Bd. 8, No. 2, pp. 



142-144, PI. IV, figs. la-c. (Described and discussed in German as a new species.) 

 Obolus apollinis Eichwald, de Veeneuil (in part), 1845, GSologie de la Russie d'Europe, by Murchison, de Verneuil, 



and de Keyserling, vol. 2, pt. 3, pp. 290-292. (Described and discussed in French. The reference includes 



Obolus (Miclnintzella) siluricus, Obolus (Acritis) antiquissimus, Obolus apollinis, and Obolus apollinis ingricus, 



Obolus apollinis being figured.) 

 Aulonotreta sculpta Kutorga, 1848, Verhandl. Russ.-kais. min. Gesell. St. Petersburg for 1847, No. 12, pp. 282-283 



PI. VII, figs, lla-d. (Described and discussed in German as a new species.) 

 Obolus apollinis Eichwald, Davidson (in part), 1853, British Fossil Brachiopoda, vol. 1, Introduction, No. 3, PI. IX, 



fig. 285 (not figs. 280-284, which represent Obolu.s apollinis). (No text reference. Fig. 285 is copied from 



Kutorga's figure, 1848, PI. VII, fig. lib, of Aulonotreta sculpta.) 



a The synonymy for this subgenus does not give a complete record of the various genera under which the species now included in Acritis 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: 



Obolus (Lucina) Eichwald [1843, p. 142]. I Obolus Siemiradzki[1886, p. 672). 



Obolu.^ de Verneuil [1845, p. 290]. Acritis Gagel [1890, p. 22]. 



Obolus Eichwald [1859, PI. XXXVII, figs. Sa^dJ. | Acritis Hall and Clarke [1892, p. 82]. 



