110 Milne Edwards on a Fossil Crustacean of the Order Isopoda. 



XVI. — On a Fossil Crustacean of the Order Isopoda^ discovered 

 by the Rev. P. B. Brodie in the Wealden formation of Britain. 

 By M. Milne Edwards*. 



[The discovery by the Kev. P. B. Brodie of fossil Isopoda in com- 

 pany with Insects in the Wealden beds of the Vale of Wardour 

 is briefly noticed in the 'Geological Proceedings/ vol. iii. pp. 134, 

 780, and in the 'Ann. Nat. Hist.^ vol. xi. p. 480. A full account 

 of these curious remains will be given in the work on the Fossil 

 Insects of the British secondary strata which Mr. Brodie is about 

 to publish (see 'Ann. Nat. Hist.^ vol. xiii. p. 63), and in the mean- 

 time the following notice of the Isopoda, by M. Milne Edwards, 

 may interest our readers.] 



Fossil Crustacea of the great division of Edriophthalmia have 

 been but recently discovered by geologists, a very smaU number 

 only being yet known, and that in a very imperfect manner. It 

 appeared to me, therefoi-e, to be desirable to indicate here the 

 existence of two new species by which the museum of the Jar- 

 din des Plantes has been recently enriched. 



The first of these was discovered in the Vale of Wardour in 

 England by the Rev. P. B. Brodie, who has had the kindness to 

 send me some specimens, and to request me to describe them. 

 This species occurs in the Wealden beds of the county of Wilts, 

 and appears pretty abundant in some localities. The specimens 

 sent me by Mr. Brodie are about 12 centimetres long and 9 

 broad, but that gentleman has found some which are consi- 

 derably larger, and which have, he says, nearly the dimensions of 

 a small Trilobite. The body of these Crustaceans is very Hat, 

 and is composed of a series of segments terminated posteriorly 

 by a sort of rounded buckler. Unfortunately the head is much 

 injured in all the individuals which I have seen. I have not 

 been able to perceive any traces of feet, but Mr. Brodie has de- 

 tected them on other specimens, and I believe I can distinguish 

 vestiges of the impressions left by the antennae. I have no 

 doubt then as to the order to which this fossil belongs ; it is evi- 

 dently an Isopod, and judging from its general conformation, it 

 ought to be ranged in the family of the Cymothoidce. I cannot, 

 however, refer it to any of the genera hitherto established, and 

 it appears to me that it cannot even be classed in any of the 

 tribes of which this great division of the Edriophthalmia is com- 

 posed. It seems to be intermediate between the genus Se?-olis 

 and the erratic Cymothoidce. It approaches the former in the 

 enlargement of its body and the great development of the lateral 

 or epimeral pieces compared to the medial or tergal lobe of the 

 thoracic and abdominal rings, as well as in the lamellar form of 

 * Translated from the Annales des Sciences Naturelles. 



