116 G. F. MATTHEW : ILLUSTRATIONS OF 



or parts of this species appear to have beeu found, so that it can hardly be used for com- 

 parison with other species. 



In the same year that Barrande published his great work, appeared Angeliu's " Palse- 

 ontologia Scandiuayica " (Part I) in which he described another large Paradoxides (P. 

 Forchammeri) which is of interest as having points of resemblance to the species which 

 forms the subject of this paper. 



1859. — At this date, Mr. J. W. Salter of the British G-eological Survey described 

 another great trilobite found by Mr. Bennett, in Newfoundland. ' This species is remark- 

 able for its extraordinary breadth, and peculiar genal spines. But while the species des- 

 cribed is larger than the example of the Braintree trilobite upon which Mr. Green founded 

 his species, it is not as large as examples since found at Braintree. The Newfoundland 

 species is, however, of greater interest to us, because in its broad form, flattened pleurae, 

 and other characters, it approached nearest to the great Acadian species which I am about 

 to describe. 



1864. — In this year, the same palaeontologist (Mr. Salter) introduced to the knowledge 

 of the scientific world another great Paradoxides, which had been found by Dr. Henry 

 Hicks in the Cambrian rocks of Wales. - The specimens figured by him are about 2| 

 inches wide at the thorax, 4 inches across the head and *7 inches long, or including the 

 extravagantly prolonged posterior thoracic segments, 10 inches long. Mr. Salter states 

 that there are fragments which indicate that this species grew to a length of 16 to 18 

 inches ; but it seems probable that in these estimates the long caudal spines are included ; ' 

 if these are omitted from the count, the length of the body would be about 12 or 13 inches, 

 which is not very much in excess of the length of P. Tessini and P. Forchammeri, the 

 largest Scandanivian species (llj to 12 inches). 



All the preceding great trilobites are of the genus Paradoxides, and flourished in the 

 Cambrian age. I may now refer to some great trilobites of the Second Fauna which rival 

 these in size. 



1824. — Dr. DeKay at this time described an American trilobite as Isoteliis gigus 

 which, however, appears to have been only a variety of the earlier known Asaplms plnty- 

 cephahis of Europe. From a fragment of this species, obtained by Prof James Hall in New 

 York State, it is estimated that it attained a length of 18 inches (45.7 cm.) 



1842. — A variety of this species or a related species {Asaphus megistos, Locke), which 

 lived on to a later period in the region to the west of New York, is estimated to have 

 attained a length of 20 inches (50.1 cm.), and was nearly a foot broad ; but no complete 

 individual of this immense size, or of similar size, in the nearly related Isotelus gigas has 

 been met with. It is clear, however, that trilobites of this type are the largest known. 



18*72. — In the year here cited, the supplement of Mr. Barrande's great work on the 

 Silurian System in Bohemia appeared. In this volume, ' he mentions the discovery by 

 Mr. Edward de Verneuil, of a great trilobite, an Asaphus, exceeding in length any of the 

 species above mentioned, except these great Asaphi, since it is said to have had a length 

 of 40 cm. (15J inches). Of this, Mr. Barrande says : " Among all the species which we 



' Quart. Jour. Geol. Soc, xv. 553. '•' Quart. Jour. Geol, Soc, xx. 233, No. 79. 



■' They are thus included in the measurement of the length of the Scandanivian species of Paradoxides, P. 

 Tesdni and P. Forchammeri. 



* Syst. Silur. Bohem. vol. i. Supp. pp. 203-4. 



