358 THE PALEONTOLOGY OP MINNESOTA. 



[Neotremats 



Order NEOTREMATA, Beecher. 

 Sub-order DAIKAULIA, Waagen. 



Family SIPHONOTRETID^], Kutorga. 



Genus SIPHONOTRETA, De Verneuil. 



1845. Siphonotreta, DE VERNEUIL. G<5ol. de la Russia d' Europe et des mont. de 1'Oural, p. 286. 

 1892. Siphonotreta, HALL. Palaeontology of New York, vol. viii, pt. i, p. 110. 



Description. "Shell elongate-oval, inequivalve; valves inarticulated. Pedicle- 

 valve the more convex, with a straight, elevated, conical, and perforated beak, the 

 circular foramen opening at the apex and communicating with the interior of the 

 shell by a tubular canal, which narrows slightly as it passes inward. No cardinal 

 area or deltidium is present, the growth-lines passing between the beak and the 

 posterior margin as elsewhere on the shell. Brachial valve depressed-convex; beak 

 marginal; posterior margin regularly arched and thickened. Interior of pedicle- 

 valve with muscular impressions confined to the umbonal region. Close alongside 

 the opening of the sipho, just within the cardinal margin, lie two elongate scars 

 which are accompanied on either side by broader somewhat expanded or flabellate, 

 simple and less distinct impressions. Directly in front of the middle pair lies a 

 small central scar, in the axis of the shell, and at either side of it a transversely 

 elongate impression. These latter impressions are distinctly separated from the 

 former by a transverse ridge. 



"In the brachial valve the impressions are equally concentrated, the entire 

 muscular area being bounded on the posterior margin by a prominent ridge which, 

 at the sides, merges into a compound lateral scar. The central portion of the area 

 is much depressed and is divided axially by a narrow ridge or septum. 



"Shell ornamented with concentric lines and ridges, the epidermal layer bearing 

 hollow spines, which are distended at the base. Shell-substance calcareo-corneous, 

 the layers beneath the epidermis being punctured by radiating and branching tubules, 

 these layers are concentric and not parallel to the internal surface. 



"Type Siphonotreta unguiculata Eichwald sp." (Hall, op. cit.) 



SIPHONOTRETA? MINNESOTENSIS Hall. 



PLATE XXIX, FIGS. Z\ and 24. 



1892. Siphonotreta? minnesotensis HALL. Palaeontology of New York, vol. viii, pt. i, pp. 112, 177, 



pi. 4, figs. 37, 38. 



Original description: "Shell subovate in outline. Pedicle- valve more convex 

 than the brachial, slightly flattened along the median line, sloping with equal 



