990 THE PALEONTOLOGY OF MINNESOTA. 



LLophospIra (?) trochonemoides. 



which the lines of growth are recurved is comparatively thia and sharp with the lines continuing without 

 interruption over the summit. (See pi. LXXVII, flg. 38.) In the Trochonernoides section of Lophospira 

 on the other hand, the angle at the end of which we find the notch, is thick and carries a true pleuroto- 

 marian band of which it is probably unnecessary to say that it interrupts the continuity of the lines 

 of growth. 



Phanerotrema, proposed by Fischer for species of the type of Pleurotomaria labrosa Hall, also reminds 

 one in a general way very strongly of these shells. That the latter have a large umbilicus and P. labrosa 

 none, is probably not of much consequence, but there are other differences that doubtless are of greater 

 importance. Of these we will point out only one, namely, the long apertural slit which occurs in Phaner- 

 otrema and is wanting in Lophospira, and which of itself is considered sufficient to warrant a generic 

 separation. 



Formation and locality. Lower part of Trenton period (?Chazy) near Knoxville, Tennessee. We 

 owe the opportunity of describing this as well as the following two equally interesting species to their 

 discoverer, Prof. J. M. Safford. 



LOPHOSPIRA (?) TROCHONEMOIDES, n. sp. (Ulrich.) 



PLATE LXV, FIGS. 41-44. 



Hight 22 mm.; width 23 or 24 mm.; apical angle 100; volutions four and a half; general appearance 

 of shell decidedly like Trochonema bellula Ulrich. Upper peripheral carina thick, rounded, lower carina 

 moderately distinct and sharp except on the latter half of the last whorl on which it grows gradually 

 weaker until at the aperture it is quite obsolete; outer two-thirds of upper slope distinctly concave, 

 remaining third flat to the suture; umbilicus large, only moderately steep, at first sharply outlined by a 

 ridge which gradually becomes indistinct and at the same time moves outward causing the slope to the 

 bottom of the umbilicus to become proportionally more gentle. Surface markings and aperture about as 

 in L. knoxvillensis, from which the present species is distinguished by its smaller size, more slowly enlarg- 

 ing volutions, relatively larger umbilicus and by the upper carina which is wanting in that species. 



As L. trochonemoides occurs at the same locality and geological horizon as Troclionema bellula, and as 

 the two might very easily be confounded by persons not thoroughly accustomed to separating fossil Gastro- 

 poda it may be well to point out some of the differences. First, both the lower peripheral and umbilical 

 carina; are stronger and more persistent in the Trochonema; then the space between the upper carina and the 

 suture line Is concave instead of flat; finally, the upper of the peripheral carinse is not so thick and 

 sharper than it is in the Lophospira, while the lines of growth, since there is no slit-band, pass over its 

 summit without interruption. 



Formation and locality." Central limestone" of the Stones Biver group, Murfreesboro, Tennessee. 

 LOPHOSPIRA (?) NOTABILIS, n. sp. (Ulrich.) 



PLATE LXXII, FIGS. 33-35. 



Hight and width nearly equal, a full grown specimen measuring about 27 mm., a small one 19 mm.; 

 apical angle about 87; volutions five. Shell like that of a Trochonema, with a moderate umbilicus, oblique 

 aperture, and strongly carinated whorls, the last partly free in old specimens. Upper carina very strong 

 and prominent, situated midway between the suture and slit-band; lower peripheral carina also unusually 

 strong and prominent; midway between these carinae, and separated from them by concave spaces but 

 little wider than itself, is the broad and salient slit-band, composed of comparatively distant, convex 

 imbricating lamelhc, averaging on the last whorl about seven in 10 mm. The top of the whorls (i. e. the 

 space between the suture and the upper carina) is flat and the base moderately ventricose with an obscure 

 carination around the umbilical depression. The aperture is oblique, more rounded than angular, and 

 abruptly notched at the extremity of the slit-band; the peristome is entire, the lower portion thick. The 

 surface markings consist of rather coarse and irregular lines of growth. These, in crossing the whorls 

 from above downwards, are not much recurved until just before they reach the slit-band. On the concave 



