Geological Society. 153 



again, the pectines slope much more than the stigmata, the 

 genital aperture having been secondarily (and since the disap- 

 pearance of the abdominal limbs) further pushed forward, 

 almost totally obliterating a sternal area usually found in 

 front of the genital opercula in those genera in which the 

 pectines have only a moderate slope. 



I refer again to my paper in ' Nature,' above cited, for some 

 of the bearings of these vestigial stigmata on the primitive 

 morphology of the Arachnida. 



PEOCEEDIJfGS OF LEARNED SOCIETIES. 



GEOLOGICAL SOCIETY. 

 March 7, 1894.— Dr. Henry Woodward, F.R.S., 

 President, in the Chair. 

 The following communications were read : — 

 1. ' The Systematic Position of the Trilobites.' Bv H. M. Pernard, 

 Esq.,M.A.,F.L.S.,F.Z.S. 



The Author, in his work on ' The ApodidiE,' endeavoured to 

 show that Apus was the ancestral form of all existing Crustacea 

 except the Ostracoda, and as such might be expected to throw Hght 

 upon the trilobites. Since the publication of this work he has 

 been studying the organization of the trilobites themselves, aud the 

 results are given in the present communication. He discusses the 

 great variability in the number of segments shown by the tri- 

 lobites ; the formation of the head by the gradual mcorporation of 

 trunk-segments ; the bending round ventrally of the iirst segment ; 

 the ' wandering ' of the eyes ; the existence and modification of the 

 ' dorsal organ ' ; and especially the character of the limbs. 



As a result of this discussion, he states that the zoological position 

 of the trilobites can now be fixed with considerable probability. 

 The features described serve to connect the trilobites with Ajjus. 

 Apus must be assumed to lie low in the direct line up from the 

 original annebdan ancestor towards the modern Crustacea, and the 

 trilobites must have branched off laterally from this line, either 

 once or more than once, in times anterior to the primitive Apus, 

 as forms speciabzed for creeping under the protection of a hard 

 imbricated carapace, obtained by the repetition on every segment of 

 the pleurae of the head-segments, which together form the head- 

 shield. 



The trilobites may be briefly described as fixed specialized stages 

 in the evolution of the Crustacea from an annelidan ancestor with 

 its mouth bent round ventrally, so as to use its parapodia as jaws. 



2. ' On the Discovery of MoUuscs in the Upper Keuper at 

 Shrewley, in Warwickshire.' By the Rev. P. B. Brodie, M.A., F.G.S. 

 Mr. R. B. Xewton read a paper at the meeting of the British 

 Association at ^'ottingham in 1893, on some lumellibranchs found 

 at Shrewley by the Author of the present paper and Mr. Richards. 

 In this paper details of the section where the shells were found are 

 given, and their interest and importance pointed out, no shells 

 having been previously detected anywhere in the Xew Red Sand- 

 stone in this country. 



Ann. cfc Mag. N. Hist. Ser. 6. Vol. xiv. 11 



