358 
THE PALEONTOLOGY OF MINNESOTA. 
[Neotremata 
Order NEOTREMATA, Beecher. 
Sub-order DAIKAULIA, Waagen. 
Family SIPHONOTRETID^, Kutorga. 
Genus SIPHONOTRETA, De Verneuil. 
1845. Siphonotreta, De Verneuil. G6o1. de la Russia d' Europe et des mont. de I'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. vShell-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 unguiculnta Eichwald sp." (Hall, op. cit.) 
Siphonotreta? minnesotensis Hall. 
PLATE XXIX. FIGS. Zi and 24. 
1892. Siphonotreta? minnesotensis Hall. PaliBontology of New York, vol. viii, pt. 1, 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 
