1870.] 



U1LLIN09 — LOWER-SILUUIAN TK1L0BITK8. 



4«1 



A Khort notice of the spi'cinKJii was drawn uj) and read liotbro the 

 Natuial-ltislory Society ot'Montreal iti 18<)4. IMihlicutioii, however, 

 was (Icl.'iyed, partly because 1 hoped to ot)tain addiliouul (.'vidence, 

 but principally heenusc I wished to have tlie s])ecim»m first exhi- 

 bited tc) the (ieological Socii^ty, and examined by .is many of the 

 Fellows as possible-. Feelinfj; somewhat a]t]»rehtnsiv(f that it would 

 be ditlicidt to pcrsuad*' geolo^;ists and ])aheinitolo}}:ists into tlu^ belief 

 of the existence of tiilobitic le.n's by tijrures and descriptions alone, 

 I thouffht it better to wait until the [)apcr and the specimens could 

 be laid before tlie So(!iet} at the same time. 



During the six years thai have elapsed, a vast number of Trilo- 

 bites have passed thron<j:h my hands, but nearly all of them in a 

 frafrmentar} eonditioTi. Among such, 1 am satislied, we may seek 

 in vain for any traces of locomotive organs. We can only expect 

 to tind tlieiu in ])erfect or nearly peif'Ct specimens. These latter, 

 considering the prodigious multitude o{ these animals that must 

 have existed in the Silurian and Devonian soas, are not abundant 

 fossils ; at least they are not so in our Canadian rocks. For ex- 

 ura])le, during the twenty years that 1 have colkcted fossils, I do 

 not believe th 'it F have seen tifty ajteciinens of ^4. plat tic''p!i(if its with 

 Avith the head, thorax, and pygidium all in connexion. \Vc have 

 had a munber of those belonging to the jnovincial collection cut up 

 and polished, without any success whatever. They were not the 

 l>est ones, but they were as perfect as was the subject of this notice 

 b(!fore it was split apart. There are others in the collection whi' h 

 may have the underside preserved ; but avc do not like to Hacnlice 

 them. Although no additional evidence of the existence o .mbs 

 was discovered, several points in the structure of other pai w<;re 

 ascertained, which will be described further on. As Sir W. E. Lo- 

 gan is about visiting London, and has kindly offered to take charge 

 of this ]ia]H'r, and will also take the specinu^ns with him, I shall 

 delay publication no longer. 



2. Diacoverij of the Fandenan Organ* in several American apedes 



of Asu])hus. 

 The evidence afforded by the spticimen above described, and others 

 of which T have made sections, proves that in the genus Axophits 

 the underside was not tlat, but soinewh".t concave. In the head, ou 

 each side of the mouth, then; was a cavity like that which occurs in 

 the existing king crab — Llmnhis Pohqiht ntus. The position of these 

 cavities is at e c, in VI. XXXL lig. J. They arc partially filled uj) 

 in the specimen ; but I havi- ascertained their depth to be about five 

 lines in another individual of the same size. The ends of the 

 plei'-iO) projected downwards a short distance below the level of the 

 sternum. The pygidium was also concave at the sides, with a por- 

 tion along the middle, holding the intestiiKS convex. This structure 

 can be seen, in part, by examining the slab from which the specimen 



* Dr. Volbortli rnlls tlie organs ii: qiiostion "<//> I'liMhrfcfun Ort/ane," a term 

 of which T hciirtily approve, us. if fionordly adoyttod, it will permanently asso- 

 ciate Dr. Pander s liamc widi his discovery. 



