78 Dr. S. Woodward— On the Structure of TriloUtes. 



I hope I Lave pointed out sufScient to prove that the relation between 

 cause and effect is borue out, as I proposed to show, and that the 

 levelling of mountain ranges may on good grounds be considered to 

 be the cause of warmth of climate, just as their elevation is productive 

 of cold. 



Buccal organs of Asaphus 

 platycephttlus, Stokes. 



V. — On the Structure of Trilobites. 

 By Henry Woodward, LL.D., F.E.S, 



IN the Geological Magazine for July, 1871, Plate VIII. pp. 289- 

 294, I published an article on the above subject, giving my 

 views of the appendages of Trilobites, and reproducing the figure of 

 Asaphus platycephaliis, Stokes, showing ti'aces of eight pairs of loco- 

 motory appendages, discovered by Mr, Billings in the Trenton Lime- 

 stone, city of Ottawa, and described and figured by him (in Quart. 

 Journ. Geol. Soc. 1870, pp. 479-486, and plates xxxi. and xxxii.). 

 I also appended a note to Mr. Billings's paper {op. cit. 1870, pp. 486- 

 488) on a palpus of Asaphus from the same locality, which is as 

 follows : — "Having been requested by Sir William Logan to examine 

 the Trilobite sent over by Sir. Billings from Montreal, I was led to 

 compare it with certain specimens in the British Museum collection, 

 presented by Dr. J. J. Bigsby, F.E.S., some years since. 



I was at once attracted by a specimen of Asaphus, from the Black 

 Trenton Limestone (Lower Silurian), which has been much eroded 



on its upper surface, having the hypo- 

 stoma, and what appear to be the ap- 

 pendages belonging to the first, second, 

 and third somites, exposed to view, 

 united along the median line by a longi- 

 tudinal ridge. 



The pseudo - appendages, however, 

 have no evidence of any articulations. 

 But what seems to me to be of the 

 highest importance, as a piece of ad- 

 ditional information afforded by the 

 Museum specimen, is the discovery of 

 what I believe to be ihe jointed palpus of 

 one of the maxillas (Fig. 1), which has 

 left an impression upon the side of the hypostoma — just, in fact, in 

 that position which it must have occupied in life, judging by other 

 Crustaceans which are furnished with an hypostoma, as Apus, 

 Serolis, etc. 



The palpus is 9 lines in length ; the basal joint measures 3 lines, 

 and is 2 lines broad, and somewhat triangular in form. 



There appear to be about seven articulations in the palpus itself, 

 above the basal joint, marked by swellings upon its tubular stem 

 which, is one line in diameter. 



There can be no reason to doubt that the Trilobita possessed an- 

 tennules, antennas, mandibles, maxillge, and maxillipeds, as we find 



h. hypostorae ; p. palpus ; 

 m. maxilla. 



