272 EMMERICH ON THE MORPHOLOGY, CLASSIFICATION 
I am not aware of a more suitable place in the system for ~ 
Calymene equalis von M. (P\.1V. fig. 6.) (from the slates of Her- 
born, the number of joints of the body of which are as yet un- 
known) than the present, but it bears about the same relation to 
the preceding as to the number of the rings of the axis of the tail, 
as Phacops macrophthalmus to Dalmania. 
Family II. AsaphiimKyes with a smooth horny membrane. 
Facial suture terminating at the posterior margin. Body from 
7 to 10-jointed. 
This family contains Brongniart’s genera Ogygia and Asaphus, 
after excluding the species considered as belonging to Phacops. 
It is distributed like the preceding through all the divisions of 
the transition rocks, with the exception of the Paradowides slate 
and the lower sandstone of the North, but it is more abundant 
in species and genera in the lower strata. 
A. Asaphi in the restricted sense. Contractile species. Fins 
always sharpened at the anterior margin, generally obtuse 
at the extremity. 
III. Griffithides, Portl. Glabella tumescent, clavate. Thorax 
9-jointed. Caudal shield furnished with 10 joints and up- 
wards.—Coal measures. Mountain limestone. 
Gr. globiceps, Phill. (Pl. IV. fig. 11.), longispinus, Portl., 
obsoletus, Phill.—Coal formation of Altwasser, &c. of Upper 
Silesia. 
IV. Gerastos, Goldf. (Proteus, Stein.) Glabella truncate, cylin- 
drical, indistinctly lobed. Thorax 10-jointed. Tail less and 
indistinctly jointed. 
G. concinnus, Dalm., &c. In the younger Silurian and 
in the Devonian strata, and perhaps also in the Carbonife- 
rous limestone (Visé). 
V. Asaphus, Brong. Glabella well-defined, clavate until it dis- 
appears ; the articulation of the tail is likewise distinct or 
indistinct until it disappears completely. Body 8-jointed. 
The species belonging to this genus have been divided into 
several genera, which are certainly readily distinguishable in 
their extreme forms, but are connected with one another by in- 
termediate members. Professor Goldfuss divides them into the 
four genera, Cryptonymus, Isotelus, Nileus and Symphysurus, 
which however only differ in certain degrees. Asaphus is a cha- 
racteristic genus for the older Silurian formations, together with 
the following. 
