THE SCOTTISH SILURIAN SCORPION. 311 



structure of the appendage of the second somite of the 

 mesosoma. 



If the above-given interpretation of the arrangement of 

 the parts constituting the ventral side of the prosoma is 

 correct — and I do not think it is likely to be very far wrong 

 — Palasophonus occupies an iutermediate position between 

 Limulus and the Eurypterida on the one hand, and recent 

 scorpions on the other, standing, if anything, rather nearer 

 to the former than to the latter. 



The same may be said of the structure of the second 

 mesosomatic appendage, which with its outer and inner 

 branch is like the corresponding appendage in Limulus; 

 while the outer branch itself, although in general form and 

 size resembling the pecten of a scorpion, offers some inte- 

 resting structural features in which it differs from that oro-an, 

 and resembles the outer branch of a mesosomatic limb of 

 Limulus. 



On the whole, it must be admitted that Palaeophonus 

 Hu uteri supplies a few more links to the chain of evidence 

 pointing to the descent of the scorpions from marine Liinu- 

 loid ancestors. 



EXPLANATION OF PLATE 19, 



Illustrating Mr. Pocock's paper on "The Scottish Silurian 

 Scorpion" (Palaeophonus Hunteri). 



The figure gives a magnified view of tlie specimen of Palseoplionus 

 Hunteri, Pocock, from tlie Upper Silurian of Lesmaliaso, Lanarkshire. If 

 was formerly in tiie collection of Dr. Hunter, and is now in the Kilmarnock 

 Museum. This lithogra|)li was executed from the s|)ecimen itself by Miss 

 G. M. Woodward, under the supervision of Mr. R. I. Focock, in October, 

 1900. 



I — VI. Prosomatic appendages, si. Sternal area of prosoma. ye«. Genital 

 cleft, pect. Pecten, or external branch of appendage of second somite of 

 mesosoma. end. Internal branch of appendage of second somite of meso- 

 soma. sup. lat., inf. lal., inf. med. Superior lateral, inferior lateral, and in- 

 ferior median crests of fourth somite of metasoma. 



