no. 1646. REVISION OF BEYBIOHIIDM—XJLRWH AND BASSLER. 285 



subglobular.. as large or larger than either of the ordinary lobes, 

 arising from the ventral part of the posterior lobe, hence located 

 wholly or mostly behind the middle of the valve. A flange-like bor- 

 der around the ends and the ventral side. This may be narrow or 

 wide, simple or rimmed, and variously ornamented with granules or 

 spines. The flange overhangs the real contact edges which are bev- 

 eled inward, the opposite edges meeting either flush or that of the 

 right valve very slightly overlaps the edge of the left. Surface of 

 valves smooth, granulose, punctate, or reticulate, or granulo-reticulate. 

 The following species have the characters of the genus as here 

 restricted : 



OKDOVICIAN SPECIES. 



Beyrickia (Steusioffia) acuta (Bey- Beyrichia (Steusloffia) signata (Bey- 



richia erratica, var. acuta Krause). 



Beyrichia (Steusloffia) antiqua (Bey- 

 richia antiqua Steusloff). 



Beyrichia granulifera, new name (Bol- 

 lia granulosa Krause). 



Be u richia (Steusloffia) linnarssoni 

 (Strepula linnarssoni Krause). 



richia signata Krause). 

 Beyrichia tvmida i CtenobolMna lu- 



mida Ulrich). 

 Beyrichia v-scripta (Bollia v-scripta 



Krause). 



SILURIAN SPECIES. 



Beyrichia adini.rta Jones and Holl. Beyrichia 



Beyrichia aequilatera Hall. Beyrichia 



Beyrichia baueri Reuter. Beyrichia 



Beyrichia baueri tripartita Renter. Beyrichia 



Beyrichia (Steusloffia) beyrichioides Beyrichia 



(Strepula beyrichioides Jones and Beyrichia 



Holl). Beyrichia 



Beyrichia bolliana Reuter. Beyrichia 



Beyrichia bronni Reuter. subspiss 



Beyrichia buctiiaiia Jones. Beyrichia 



Beyrichia buctiiaiia angustata Reuter. Beyrichia 



Beyrichia buctiiaiia incisa Reuter. Beyrichia 



Beyrichia buctiiaiia tata Reuter. Beyrichia 



Beyrichia buctiiaiia nutans Kiesow. Beyrichia 



Beyrichia eta rata Kolmodin. Beyrichia 



Beyrichia damesi Krause. Beyrichia 



Beyrichia diffusa Jones. Beyrichia 



Beyrichia dubia Reuter. Beyrichia 



Hey rictt ia grandis Kolmodin. Beyrichia 



Beyrichia granulosa a Hall. Beyrichia 



Beyrichia intcrrupta (Bollia inter- Beyrichia 



rupta Jones). Beyrichia 



Beyrichia jonesii Boll. Beyrichia 



tdrrdeni McCoy. 

 Icloedeni acadica " Jones. 

 klocdeni antiquata Jones. 

 klcedeni bicuspis Kiesow. 

 Jcloedeni granulata Jones. 

 klcedeni infecta Jones. 

 Mcedeni intermedia Jones. 

 klcedeni intermedia, subvar. 

 a Jones and Holl. 

 Ida den i iiuda Jones. 

 Mcedeni protuberans Roll. 

 Icloedeni subtorosa Jones. 

 klcedeni torosa Jones. 

 klcedeni verruculosa Jones. 

 kochii Boll. 

 tata a Hall. 

 lauensis Kiesow. 

 lindstromi Kiesow. 

 maccoyiana Jones. 

 maccoyiana sulcata Reuter. 

 moodeyi, new species. 6 

 muldensis Chapman. 

 nodulosa Boll. 



American species. 



6 This species is very similar to B. maccoyiana and is probably the American 

 form referred to this latter species by Jones. It is distinguished by the greater 

 isolation of the median lobe and the very finely punctated surface of the lobes. 

 See Plate XXXVII, fig. 8. 



Formation and locality. — Cayuga formation, near Cacapon, West Virginia. 



Cotypes.— Cat. No. 53936, U.S.N.M. 



