276 EMMERICH ON THE MORPIIOLOGY, CLASSIFICATION 
XX. Cryptolithus, Green (Trinucleus, Murch.). Glabella cla- 
vate, divided into lobes at the sides. Thorax with six seg- 
ments. Caudal shield articulated. Eyes? Characteristic 
for the older Silurian rocks, less frequent in the younger. 
Cr. granulatus, Green, Caractaci, Murch., &c. 
XXI. Ampyx, Dalm. Only distinguished from XX. by the ab- 
sence of the reticulate foveolate broad margin. Facial su- 
ture? Contractile. 
A. nasutus, rostratus, Sars, mammillatus, Sars. 
Harpes, Goldf. differs from Trinucleus by the greater number 
of rings of the thorax, which latter however cannot be distin- 
guished from those of the articulated tail.— Devonian. 
Section II. All the segments of the body at the posterior part 
of the cephalic shield are homologous and moveable: only the 
last (rectum) joint is without fins. They are the Myriapoda 
among the Trilobites, but are not so isolated as the former; on 
the contrary, we may say that they approximate to the Calymene 
through Amphion, to the Trinucleit through Harpes, and finally, 
to the Odontopleure through Odontopleura centrina. Only one 
family. 
Family VI. Oleni. 
XXII. Olenus. Cephalic shield cornuted. Facial suture ter- 
minating at the posterior margin. Glabella clavate, divided 
into lobes. Eyes hiant, with an upper eyelid. Body (at 
least when aged) 20-jointed, with a scaly-formed rectum 
joint. The Oleni probably underwent a metamorphosis in 
as far as the number of thoracic rings increased with age.— 
In the oldest Silurian rocks. 
Ol. Tessini, C. 
XXIII. Remopleurides, Portl., differs from XXII. only by a 
lesser number of rings (12), and by the fins being very short 
in proportion to the axis; in all other respects they corre- 
spond entirely with those of the preceding genus.—Irish 
Silurian transition rock. 
R. Colbii (Pl. IV. fig. 13.), longicaudatus, latert-spinifer. 
Supplement XXIV. Ceraurus, Green. 
XXV. Agnostus, Brong. (Battus, Dalm.), pisiformis, Brong.— 
Lowest Silurian rock. 
