DESCRIPTION OF GENERA AND SPECIES. 173 
connection with the illustration given by Doctor Owen leads me to think that the 
genotype was a fragment of the cranidium of Owen’s Dikelocephalus granulosus, 
illustrated by figure 7, plate 1 [Owen, 1852]. This, however, can not be proven, 
so I will accept Owen’s definition and include under the genus a group of species 
having a strongly convex glabella, with a narrow frontal limb and border and 
broadly rounded front; tumid fixed cheeks, small eye-lobes, granulated surface, and 
very faint or no glabellar furrows. 
The species are more or less provisionally referred, as only the central portions 
of the cephalon are preserved. Further study, or the study of more perfect speci- 
mens, will undoubtedly lead to the reference of some of them to other genera. 
Neither of the species referred to Menocephalus by E. Billings appears to belong 
to the genus. They are: 
Menocephalus sedgwicki Billings [1865b, p. 407] = Solenopleura; 
Menocephalus glabosus Billings [1865b, p. 408] = Solenopleura. 
Menocephalus saltert Devine (Billings, 1865a, p. 203] is the type, an undescribed 
genus. 
Menocephalus abderus (Walcott). 
Plate 16, Figure 3. 
Solenopleura abderus WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xx1x, p. 88. (Species characterized 
as below.) 
This species is represented by the glabella, occipital ring, fixed cheek, and 
frontal rim. It is most closely related to M. acanthus, but differs in the nar- 
rower fixed cheeks and short, rounded frontal rim. The surface is also marked 
by larger and many more pustules, which are scattered more or less irregularly 
over the surface. Three pairs of short glabellar curves are faintly indicated upon 
the rounded sides of the somewhat convex glabella. The type specimen has a 
length of 8 mm. and a large cephalon associated with it of 12.5 mm. 
Formation and Locality—Middle Cambrian: (C19) Uppermost layers of the 
Ch’ang-hia limestone [Blackwelder, 1907a, p. 33 (part of last list of fossils)], at 
Ch’ang-hia, Shan-tung, China. 
Collected by Li San. 
Menocephalus acanthus (Walcott). 
Plate 16, Figures 4, 4a—. 
Solenopleura acantha WaALcoTt, 1905, Proc. U. S. Nat. Mus., vol. xx1x, p. 88. (Species described as 
below.) 
General form of cephalon, exclusive of free cheeks, transversely rhomboidal, 
and rather convex. Glabella prominent, convex, truncato-conical, with width at 
the base and length about the same; a short, strong furrow marks off two small, 
subtriangular lobes at the postero-lateral angle; a second pair of slightly marked 
furrows occurs upon the sides, next to the dorsal furrow, about midway of the length 
of the glabella; the sides slope inward from the base, so as to reduce the width of 
the rounded front to about two-thirds that of the base; occipital furrow narrow, 
transverse, and deep; occipital ring narrow at the sides, broadening toward the 
center, where it is thick and convex; dorsal furrow very distinct at the sides and 
front. 
Fixed cheeks convex, but much lower than the glabella; they are about as 
wide at the palpebral lobe as the width of the glabella in front; their appearance 
of convexity is given by the downward slope toward the frontal rim and backward 
