970 THE PALEONTOLOGY OF MINNESOTA. 
(Lophospira serrulata 
specimens precisely like his in that respect. Two other features, however, shown in 
his illustrations are less easily reconciled with our specimens, and we confess that we 
can do so only by assuming that his drawings are not entirely trustworthy. Weare 
loath to admit so much variation in at least one of the characters for we have found 
it to be remarkably constant in all other species. We refer namely to the direction 
of the lines of growth. These, we believe, do not bend sufficiently backward and 
forward in Salter’s figures. In justification of our view we would point out the 
fact that his two figures (1 and 1*) are not exactly alike, so that it is not entirely 
unwarranted to assume that neither agrees exactly with the specimen. Then he 
represents the upper carina as nearer the suture than we have seen it, and farther 
from the peripheral angle than it should be if his description is correct is saying 
that the first and third keels are equally distant from the second. 
As to Murchisonia tricarinata Hall, under which name Prof. Whitfield (loc. cit.) 
referred to young examples of both ZL. serrulata and L. helicteres, we have not the 
slightest doubt that Hall’s fig. 6¢ was taken from an imperfect testiferous example 
of L. serrulata. This specimen, however, has four carine and is evidently distinct 
from the type represented by his figs. 6a and 6. It was moreover only doubtfully 
referred to tricarinata by Hall himself. The validity of the species tricarinata, 
therefore, must be determined solely by the original description and type and not 
by Hall’s second specimen which we have said is clearly referable to L. serrulata 
Salter. J. serrulata is the only species of the genus known to us having the flange- 
like peripheral keel serrated on the edge like a circular saw.* It is an excellent 
specific character, though unfortunately leaving no trace of its presence on casts of 
the interior. Still, the beds in which the species occurs in that condition are of 
such a nature that very often an excellent artificial cast of the exterior can be 
prepared from the natural mold enclosing the interior cast. The species is readily 
distinguished by other peculiarities, as may be seen by comparing it with other species 
described in this report. Some difficulty will probably be experienced in making a 
successful separation between it and the next species, L. helicteres, particularly 
when internal casts only are available. For comparisons see under that species. 
Formation and locality.—Stones River group, in the Vanuxemia bed chiefly, at Minneapolis and 
St. Paul, Minnesota, Mineral Point, Janesville, Bellville and Beloit, Wisconsin, and Dixon, Illinois. 
Also in the Black River group (Upper Buff limestone) at Beloit, Wisconsin, and in central Tennessee 
(Carter’s Creek limestone). In Canada the species occurs at Panquette’s rapids in the Ottawa river in 
strata said to be of the age of the Black River group. 
Collections.—Geological and Natural History Survey of Minnesota; E. O. Ulrich; Prof. J. M. Safford. 
Museum Register, No. 7283. 
* Prof. Whitfield on two occasions credits other species with such keels, the first time in Geol. of Wis., vol. iv, p. 221, 
where he says it is occasionally or frequently met with in Murchisonia (Lophospira) helicteres and M. tricarinata ; the second 
time in 1886, Bull. No. vili, Amer. Mus. Nat. Hist., p. 311, when he says it occurs in “Many of the specimens [of Lophospira]| 
especially of M, milleri”’ [L. bicincta.] We are convinced that in both cases he refers to specimens of the form which we 
identify with LD. serrulata Salter, since among the numerous specimens of L. helicteres and L. bicineta studied by us we have 
never observed even a semblance of such a keel, 
