576 



L 0 N C H OOKPHALUS AND OREPIOEPH ALUS. 



LONCHOCEPHALUS CHIPPEWAENSIS. (N. S.) 



(Tab. I. figs. C, 1-1; Tab. I., a, fig 9.) 



Specific character. — This very minute species of Lonchocephalus rests chiefly on its small, semi-ellip- 

 tical glabella, being little more than from one-tenth to three-tenths of an inch long; in the short spicula, 

 a spine projecting backward in the median line from the base of the glabella; in the horseshoe-shaped 

 area surrounding the glabella, and forming the cephalic shield ; in the semilunar shape of the caudal 

 shield (seen at the base of fig. 6, Tab. I.), with a very narrow border deflected downwards; the axal 

 lobe with four segments. 



This curious little Trilobite occurs by thousands in the soft gritstones of the Red Cedar or Menomonie 

 branch of the Chippewa, occupying a position in F. 1 either of the third or fourth Trilobite-bed. In a 

 slab measuring three inches square, more than one hundred individuals can be counted, but in no instance, 

 as yet, have the thoracic segments been discovered. 



LONCHOCEPHALUS HAMULUS. (N. S.) 

 (Tab. I., a, figs. 8 and 12.) 



Specific character. — All that has yet been brought to light of this species is the glabella, with its 

 remarkable appendage, and a portion of the cheek-plate. 



The glabella is convex and undivided, quadrilateral in front, tapering behind, and provided with a 

 long spine, attached to its base, and projecting, in the median line, in an arch backwards; this spine is 

 much longer in proportion than that of the preceding species, and is formed in the shape of a fish-hook, 

 as is well shown by a detached spine embedded in the medal-ruled slab, fig. 8 ; furrows of the glabella 

 almost obsolete. The facial suture, as it proceeds with a slight sigmoid flexure around the eye-plate, is 

 in close proximity to the glabella ; then slightly diverging, it circumscribes a circular area in front of the 

 glabella, proportionally greater than that of D. Minnesotensis. 



Caudal shield as yet unknown. 



This Trilobite occurs in the same light greenish-gray gritstones of F. 1 as the D. Miniscsensis, up- 

 wards of two hundred feet beneath the base of the Lower Magnesian Limestone, F. 2. 



CREPICEPHALUS. (N. G-.) 



Generic character. — Some rich Trilobite slabs, occupying the position of the third Trilobite-bed at the 

 Mountain Island section, contain numerous fragments of a Trilobite, a portion of the cephalic shield of 

 which is seen on the medal-ruled slab, fig. 16 of Tab. I. A, on the left corner, as well as by figs. 10 and 

 18 of the same plate. These, as far as preserved, approach somewhat in form to the genera Solenosema, 

 Mirropi/ge, and Endogramma ; but if the caudal shields, fig. 8 of Tab. I., and fig. 16 of Tab. I. A, corre- 

 spond, which seems improbable, as they are abundantly disseminated in the same bed, and are mineralized 

 in the same manner into a brown, ferruginous crust, contrasting strongly against the gray gritstone, then 

 this Trilobite of Mountain Island, must constitute a genus distinct from either of these, and for which 

 the name Crcp>iceph,alus is proposed.. 



The rather fiat, slipper-shaped glabella is tapering and slightly acuminated anteriorly, with a faint 

 ridge in the median line ; two small and very superficial depressions, and a posterior faint furrow, very 

 partially divide the glabella. The facial sutures run nearly parallel to the margin of the glabella, and 

 join a thickened, cord-like, anterior narrow border, enclosing a convex area, narrower in front than at the 

 sides. Oblique plications can sometimes be traced on the cheek-plate, in advance of the eye, converging 

 towards the apex of the glabella. 



If the associated pygidiums, fig. 8 of Tab. I., and fig. 16 of Tab. I. A, belong to Trilobites of this 

 species, they are relatively larger than those of any of the above genera. The axal lobe has four seg- 

 ments; side lobes bounded by a slightly concave border, which widens posteriorly, and of which the con- 

 fines are almost rectangular, with rounded corners. 



There are probably at least two species of this genus ; one about a third larger than the other. The 



