CRUSTACEA. Ill 



ital lobes are small and well defined; the occipital furrow sharp and narrow, 

 and the occipital annulation broad and flat. The anterior border is narrow, 

 thickened and curved upward. 



Surface finely tubercled. Length of the cephalon 7 mm., width between 

 the eyes. 5.5 mm. 



Observations. The fragments of this species in their general outline, reflexed 

 anterior bonier and strong basal glabellar lobes, are very similar to the same 

 parts in Proetus rnacrocephalus, of the Hamilton group, though in the latter the 

 glabella is less convex, more elongate and conate than in P. ovifrons. The simi- 

 larities which exist in the cephala of these two species, and which are also 

 observable in the pygidia of P. microgemma ami P. rnacrocephalus, may. with a 

 more complete knowledge of these Upper Helderberg forms, ultimately render 

 it necessary to unite these detached parts under one specific designation. 



Distribution. Upper Helderberg group. Corniferous limestone: In the de- 

 composed chert. Canandaigua, Ontario county. 



Proetus delphinulus, n. sp. 



PLATE XXIII. FIGS. 1,2; iM' PLATE XXV, FIG 6 



A single small, somewhat imperfect cephalon shows the following characters: 

 Outline semi-elliptical ; border very broad, its width on the anterior limb, 

 where it is slightly produced, equaling one-third the length of the cephalon: 

 along the margin it is conspicuously thickened and gently reflexed ; the mar- 

 ginal sulcus is broad and deep on the cheeks, becoming much wider on the 

 frontal area, producing a general concavity in that part : this sulcus is 

 bounded on its inner margin by a narrow ridge skirting the base of the cheeks. 

 The genal angles are produced into slender, acute spines, longer than the 

 glabella, and distinctly grooved on their upper surface by the continuation of 

 the occipital furrow. 



The facial sutures converge rapidly on the frontal area. 

 The glabella is sub-conate, and relatively small, tapering rapidly from the 

 base to the anterior extremity, which lies just within the broad frontal 



