BRACIIIOPODA. 359 
Miplionot retiiV miiinesoleiisis.] 
convexity toward the lateral and anterior margins. Foramen apical (?). Brachial 
valve depressed-convex, somewhat elevated about the umbo. Surface covered, 
in the urabonal region, with fine, anastomosing and gently undulating concentric 
lines, which, in the latter portions of the shell, are finely granulose or serrated; at 
about one-third the length coarser varieties of growth appear, between which the 
finer lines are retained. Surface covered with hollow spines of various sizes, which 
appear to have been mostly set over the umbonal region of the pedicle valve. 
Here, where the growth lines are absent, the spine-bases in the original specimen are 
large and all of about the same size, and are disposed without order. Over the oth^- 
portions of the shell the spines are set along the edges of the varices, small and large 
being indififerently mixed. The bases of the spines make annular swellings on the 
interior of the valve. The length of the original specimen is 15 ram., width, 12 mm.'' 
Since no additional material has been discovered other than that used by 
professor Hall, we give in addition his observations on the species, with its 
relations to a similar form which is tentatively referred by him to Schizambon. 
"The American palaeozoic faunas have yet furnished no thoroughly satisfactory 
representative of Siphonotreta. Before us are two specimens of a form allied to, but 
probably distinct from the Canadian representatives of Schizambon (1), referred to 
on a following page [Siphonotreta scotica Wh\tesiYes=Schizambon fissiis var. canadensis 
Ami (Hall)], which have been collected by Mr. Charles Schuchert and Mr. E. (). 
Ulrich, from the Trenton limestone at Minneapolis, Minnesota, One of these is an 
exterior mould, the other retains both val\4es, though the umbonal part of the 
pedicle valve has been broken, leaving no indication of the character of its foram- 
inal aperture. The shell differs somewhat from the Canadian specimens in outline, 
being broader over the pallial region; the brachial valve shows a low longitudinal 
depression, the shell substance is very thin, while in the other species referred to. 
it is remarkably thick, and its lamellose structure conspicuously developed; the 
ornamentation of the surface consists, not of sharp, concentric lines, broadening to 
ridges toward the margin, but of fine, concentric, anastomosing wrinkles, which are 
interrupted over the body of the shell by the edges of the spiniferous lamella?; the 
spines are comparatively short and sparse. Though recognizing the difficulties in 
the discrimination of species of Siphonotreta, we are nevertheless disposed to regard 
the above mentioned features as of specific value; and in the absence of evidence 
determining the character and position of the pedicle passage, it seems judicious to 
leave the species for the present under the genus Siphonotreta, with the designation 
Siphonotreta minnesotensis." 
Formation and locality. — From the Trenton limestone near the University of iMInnesota, Minne- 
apolis, Minnesota. 
Collectors. — E. O. Ulrich and Charles Schuchert. 
