480 



I'UOCTIKDINOS OF THE OEOLOOICAL SOCIETY. 



Fig. 



EXPLANATION OF PLATES XXXI. A XXXll, 

 Plate XXXI. 



P^ig. J. AHiij)//i(fi pliifi/n-phaliis. StokoH. — I'lidersido, showing tlii> logs; « /'• 

 Huhirn (lirotigh tho rloublurc ; f, ( . oaTitit's on cnfli side of tlic livpostonia ; 

 (/, (/. tuberclos on tlio pygidiuni ; //. (K.']>liHlic doubluro ; /, /, tin.' two IoIwm 

 of the hyj)08toina , m, position of t-he in(nith ; 7^ n, », », joints in tht- legs 

 2 Transverse ideal .'^eetion through tlie thorax ; a. h. tlie doublure of tho 

 pleune ; />, position of tlie Paiulerian organ. The dotted lino from h to h 

 indicates tlie (contour of ili«' ventral surface. 



Fig. 3. Ideal section ihrough tlie head, cutting olT the points of the hypustonia, 

 /, I, ill a plane pnssing through tho eyes ; 1, 2, position of the 1st and lind 

 pairs of legs. 



Fig. 4. .Section through tho tail of a srtiall specimen, showiig (lie doublure, //. 



Fig. 6. Three ))lenne restored, showing the po'<ition of the Pandenan organ at 

 p ; r/, '), portion of the plourie removed 



Pig. G. Supposed leg of Trilobiti^, ligured by Eicliwald : (/, natural size ; i, 

 enlarged. 



Plate XXXn, 



Fig. 1. Asaphus pla'i/oephahis. — Side view of the specimen which shows the 

 legs, somewhat restoi-ed. The dotted line, (/ c^, represents the position of 

 the piano of the Tentral surface nearly. 



Fig. '2. I^orsal view of tlm same; the dotted lines indicate tho position of the 

 hypostoma and legs. 



Fig. ,'5. Cal^iiune. scnarin. — Section through the axis of the thorax: (/, junc- 

 tion of hi»ad and tail ; h, back of the head ; r d, hypostoma ; e, end of the 

 tail ; /, a body showing strui/ture. 



Fig. 4. A group of the small bodies in lig. 'i, enlarged S diameters. 



Fig. b. The organic body seen at / in fig. 4, enlarged li diameters. 



DjSf.T'SSION. 



Mr. WooDWABi) had carefully exarnined Mr. Billings's specimen, 

 and agreed with him in considering that there wa.s nndotibtod 

 evidence of tho presence of ■walking-;ippend;ige(» nndor the thorax. 

 The presence of such limhs might a j>riori have been expected; and 

 the nature of the test anggcfsted that the Trilobites were Avalking 

 rather than swimming forms of Isopods. I'he brauchite had pro- 

 biihly been under the telson ; and thi.si woidd account for its larg(.> de- 

 velo])ment. li was not more surprising to find highly orgauizcd 

 Trilobites than it was to find such highly organized crustaceans as 

 Pferiif^otiis, Eariipieritf^ and SUinoniri in the same beds. 



Prof. Rii'Kin' Jom:s, l'riniij)al D.vwson, and Sir Wm. liOOAN 

 made some remarks, more especially on J'rotichiiites and Cliriiactich- 

 nitos — tho latter having been explained as galleries of Trilobites, by 

 Prof. Jones, when first (exhibited in England. 



. . ^.^LjliJu-uLli 



