APPENDIX. 73 



this appearance is due to the great obliquity of the ray. I wish to call attention 

 to this, because I consider it enables us to understand the nature of the enigmatical 

 puncta. If we suppose a head furnished with a produced membranous margin 

 instead of a perforate one, we shall get at the explanation by supposing the 

 membrane to collapse at regular intervals, become plicate, then perforate, and 

 lastly, separate into linear processes. Now we have in Harpes the flat border, 

 with rows of impressed puncta, which have not yet perforated the fringe. In 

 Trinucleus fimbriatus, we have a plicate border, the thin interstices of which 

 have contracted into pores, which is a step beyond the simple perforation in linear 

 series exhibited by T. omatus. Lastly, in Ceraurus (Acidaspis, Murch.), we have 

 the structure completed, the linear processes being quite separated into spines. 

 This structure is not anomalous, for the cellular membrane which forms the inner 

 peristome of the mass passes through an exactly similar course, becoming in 

 different species perforate, in others separated into distinct teeth. 



" That these perforate or spinous fringes are not essential, but only supple- 

 mentary parts of the head, may easily be shown by the fact that the width of the 

 head, without the fringe, is exactly that of the body, and when the animal is 

 doubled up the fringe projects freely on all sides. We still require to find 

 anomalous specimens in which all or some of the above modifications, plications, 

 perforations, or partially cleft borders, may be exhibited together, in order to 

 demonstrate the supposed origin of the structure " (p. 253). 



In another paragraph in the same paper Salter refers to the discovery by 

 himself and Bmmrich of the facial suture in Trinucleus omatus. " Its course," he 

 states, "is obliquely upwards from the eye tubercle to the upper end of the 

 glabella, where it appears to terminate in a solitary deep perforation, similar to 

 those which surround the head" [op. cit., p. 251). It is to these pair of deep 

 puncta, one on either side of the head, that we would specially draw attention. 



Later on (in 1852) M. Barrande, in his " Systeme Silurien de la Boheme " 

 (vol. i, Trilobites, p. 230), thus wrote: "On the antennae of Trilobites : — Prof. 

 M'Coy, in his work already cited (p. 43), announces what he deems to be the 

 discovery of the remains of antennas in the form of a deep pore on either side of 

 the frontal lobe in the groove which surrounds the glabella. He enumerates the 

 genera Trinucleus, Acidaspis, Galymene, Ampyx, Griffithides, &c, in all of which 

 this observer states he has succeeded in tracing these organs. We have also 

 remarked these puncta long since in a variety of Trilobites from Bohemia, notably 

 in Galymene, Trinucleus, Cheirurus, but we have been led to offer a different 

 interpretation to that indicated above. 



" First, we have to observe that if this cavity does not appear to be anything 

 else but a pore in those species with a border, as Trinucleus, it assumes larger and 

 larger dimensions as it approaches the edge of these Trilobites, and forms a 



