622 CAMBRIAN BRACHIOPODA. 



Talve, and in the size of the splancluiocoele. T. Icempanum is a larger shell with different vas- 

 cular and other scars in the interior of the ventral valve. Figures 2, 2a-d represent specimens 

 collected by S. Ward Loper for the United States National Museum, and figures 2e-h represent 

 the specimens in Matthew's collection, now at the University of Toronto. 



Formation and locality. — Middle Cambrian: (301 [Matthew, 1895a, p. 122]) Sandstones of Division lb2; (21i) 

 sandstones of Division lb2; and (2i and 2k) sandstones of Division lb3; all in Matthew's [1895a, p. 108] Protolenus 

 zone, on Hanford Brook, St. John County, New Brunswick, Canada. 



Genus SCHIZAMBON Waleott. 



[axKtii, I divide; and Uii^wv, a raised edge.) 



Schizamhon Walcott, 1884, Mon. U. S. Geol. Sui-vey, vol. 8, pp. 69-70. (Described and discussed as a new genus.) 



Schizambonia Oehlert, 1887, Manuel de conchyliologie, by Fischer, p. 1266. (Described in French.) 



Schizamhon Walcott, Hall and Clarke, 1892, Eleventh Ann. Kept. State Geologist New York for 1891, pp. 253-254. 



(Described and discussed.) 

 Schizamhon Walcott, Hall and Clarke, 1892, Forty-fifth Ann. Rept. New York State Museum for 1891, pp. 569-570. 



(Copy of preceding reference.) 

 Schizamhon Walcott, Hall and Clarke, 1892, Nat. Hist. New York, Paleontology, vol. 8, pt. 1, pp. 113-117. (Copies 



the original description, Walcott, 1884b, p. 69, and discusses genus and species referred to it.) 

 Schizamhon Walcott, Winchell and Schuchert, 1895, Nat. Hist. Minnesota, Geology, vol. 3, pt. 1, Paleontology, 



p. 360. (Copies the original description, Walcott, l884b, p. 69, and discusses genus.) 

 Schizamhon Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 4, PI. KI, and pp. 142 and 146. (Classification of 



genus.) 



This genus is described in Monograph VIII of the United States Geological Survey [Walcott, 

 1884b, p. 69] and very fully in Hall and Clarke's monograph [1892c, p. 113]. 



The type species is illustrated in this memoir on Plate LXXXIV. The other species 

 now referred to the genus are ;S'. ? esthonia Walcott, S. manitouensis Walcott, and S. priscus 

 Matthew. As stated in the original description [Walcott, 1884b, p. 69] Siphonotreta fissa 

 Kutorga appears to belong to the genus, and Hall and Clarke [1892b, pp. 115-116] include 

 ScMzamhonf canadensis (Ami);" Messrs. Winchell and Schuchert [1895, pp. 361 and 362] ten- 

 tatively include SJ dodgei and S.f locJcei, and Mr. George H. Hudson [1904, p. 284] describes 

 a new species, Schizamhon duplicimuratus, from the Chazy limestone on Valcour Island, Lake 

 Champlain, New York. 



Type. — ScJiizamhon ty.picalis Walcott. 



, Schizamhon? esthonia n. sp. 

 Plate LXXXIV, figure 4. 



This species is represented by a single specimen of the ventral valve. It is nearly circular 

 in outline and moderately convex. Apex a little in advance of the posterior margin; a slight 

 flattening back of the apex outlines a faint false area. A wedge-shaj^ed depression extends 

 from the sharp apex forward a short distance to its larger end where the large oval foramen 

 occurs; this depression is similar to that in Schizamhon typicalis Walcott and S.fissa (Kutorga) ; 

 it is marked by fine lines of growth back of the foramen. Surface marked by fine concentric lines 

 of growth and three narrow, low, concentric ridges or varices of growth; the entire surface is 

 finely granulated, the granules being formed apparently by the crossing of fine, curving, oblique 

 furrows that start on the posterolateral margin and curve forward obliquely across the shell, 

 crossing so as to form rhomboidal spaces in which the granules occur. This type of surface is 

 unlike the spinose surface of S. typicalis. It suggests the surface of Micromitra and some forms 

 of Oholus {Westonia). From some points of view the crossing of the depressed lines gives a 

 punctate appearance to the surface. 



It may be that this shell belongs to some other genus, but with the present information it 

 is referred to Schizamhon. 



The specific name is derived from Esthonia. 

 Formation and locality. — Upper Cambrian: (336h) Ungulite grit, at Baltischport, Esthonia, Russia. 

 a Siphonotreta scotka canadensis Ami, 1887, Ottawa Naturalist, vol. 1, No. 9, p. 124. 



