402 Prof. F. M‘Coy on the Classification of 
1. Harpgs (Gold.). 
?2. Harpipetya (M‘Coy). See below. 
?3. AmpHion* (Pand.). 
5th Subfam. AGNosTIN”. ° 
Minute, blind ; only two thoracic segments ; head and abdomen 
covered by nearly equal and similar rotundato-quadrate shields. 
This subfamily includes both the families Phalacromides and 
Battoides of Hawle and Corda, distinguished solely by the ser- 
ration or smoothness of the margin of the tail,—a pomt in my 
mind of generic value at most. 
From the absence of eyes, and the very slight powers of loco- 
motion argued by so small a number of thoracic, feet-bearing, 
rings, it occurs to me that the Agnostzne may hold the same 
position among the Trilobites that the Suctoria do among the 
Crustacea generally ; that group being similarly distinguished from 
its allies by the want of eyes, few body-rings, little or no powers 
of locomotion, and abnormally and variously shaped bodies ; 
being parasitic generally on fish. Bophyrus, the analogous group 
among the Isopod Crustacea, is always parasitic on the gills of 
the larger Crustacea, under their carapace ; and such I strongly 
suspect were the habits and mode of life of the Agnosti, iving in 
all probability attached to the gill-feet on the under side of Tri- 
lobites, some of the largest known species of which accompany 
those little animals. 
1. Trinopus + (M‘Coy)= 4Arthrorachis (Hawle and Corda). 
2. Acnostus (? British). 
Subgen. 1. Diplorhina t (H. & C.). 
* This genus and Encrinurus present some points of analogy, and may 
serve to indicate the passage from this subfamily to the Paradoxine by 
means of Zethus, but I unfortunately cannot refer to any specimens of the 
body-rings of either Amphion or Encrinurus at present, and have therefore 
some uncertainty about them. I may here remark on the great apparent 
inequality of extent or numerical value of the five groups into which I have 
distributed the great family of Trilobites, that it results chiefly from a pecu- 
liarity of geographical distribution, and in great measure disappears when 
the large number of recently described foreign genera are included: thus 
the Harpedine and Paradoxine, which seem so meagrely represented in the 
above list of British genera, acquire a prodigious development in the Silurian 
rocks of Bohemia. 
+ I originally defined this genus in 1846 in my ‘ Synopsis of the Silurian 
Fossils of Ireland,’ and pointed out its differences from Agnostus ; subse- 
quently Hawle and Corda have figured and described the group under the 
title of Arthrorachis in their ‘ Prodrom.’ on Bohemian Trilobites, without 
knowledge of what I had done, also pointing out its obvious differences from 
Agnostus (or Battus), 
i : have noticed the Diplorhina triplicata in the black Llandeilo shale of 
Builth. 
