Carpenter, The fossil Isopod {Oxyuropoda) of the Irish Devonian. 66c 



A few remains — for the most part fragmentary — of Eurypterids 

 and Leptostraca have also been found there. 



My friend and former colleague Isaac Swain, now professor 

 of geology in University College, Cork, was fortunate enough to 

 obtain there the remarkable fossil which forms the subject of 

 this communication, as well as a beautiful impression of its 

 upper surface, the rock having split along the plane in which 

 the crustacean had been imbedded. 



The general appearance of the animal, and the pair of long 

 pointed tail-appendages (uropods) which it bears, suggested at 

 once affinity to the Isopoda and even to the special group of 

 the Oniscoidea. From a study of the segmentation of the body 

 we have, I believe, been able to place the isopodan nature of 

 Oxyuropoda beyond doubt. There is a clear distinction between 

 the extensive, oval thorax and the short narrow abdomen, the 

 six segments of which can be clearly distinguished. 



According to our interpretation, the thorax consists of one 

 segment which is, partially at least, fused with the head, and six 

 free segments, each of which displays a characteristic arrange- 

 ment of transverse furrows and paired tubercles. As in the Onis- 

 coidea, the pleural region of the segments is very well developed. 

 A thoracic limb'resembling the uniramous Walking leg of a wood- 

 louse, is fairly well preserved, and a swollen structure in connec- 

 tion with the first thoracic segment may be doubtfully regarded 

 as representing a chelate appendage. 



The length of the fossil is 66 mm. 



It has already been pointed out that in Oxyuropoda we see 

 combined the characters of several divergent tribes of the Iso- 

 poda. The general build of the body recalls the appearance of 

 the Oniscoidea; the association of the first thoracic segment with 

 the head, and the possibly chelate nature of the appendages of 

 that segment suggest affinity with the Tanaidacea; the trilobitic 

 aspect of the segments, the lateral position of the uropods, and 

 the association of the first thoracic segment with the head re- 

 semble the conditions in the Serolidae, a family of the Flabelli- 

 fera. We see there fore that this Devonian isopod shows, as might 

 be expected, interesting lines of connection with several divergent 

 tribes of the order. The establishment of Oxyuropoda as a true 

 Isopod is important, since we are thus able to trace back the 

 existence of that order with certainty to Devonian times. 



Hitherto much controversy has raged as to the nature of 

 the Palaeozoic fossils — Arthropleura, Praearcturus, Amphipeltis 

 — attributed by various authors to the Isopoda. Ca Im an for 

 example has lately denied the isopodan nature of any of them. 

 Andree, on the other hand, after a careful study 1 ) of the various 



x ) Palaeontographica Bd. 7, 1910. pp. 67 — 104. Taf. IV, V. 



