496 H. Woodtoard — New British Fossil Crustacea. 



In examining a large number of genera of recent Isopoda in the 

 British Museum Collection, I noticed that the presence of a median 

 ridge or keel to the telson or terminal joint was of rare occurrence 

 in any species, the one figured in our plate being almost the only 

 example met with. This character, combined with the finely dentated 

 border of the telson, and the characteristic, punctate, and wrinkled 

 ornamentation of the surface of the segments, led me to the conclu- 

 sion that the genus Mga, offered the nearest living analogue to this 

 fossil crustacean ; and I therefore propose to name it Falcega, 

 adding the specific name of Carteri, in honour of my friend James 

 Carter, Esq., through whom I first became acquainted with this 

 interesting fossil. 



Description. — (Head and four anterior segments wanting.) Eifth, 

 sixth, and seventh, thoracic, and five abdominal segments and telson 

 present in Figs. 3, 4, and 6 (Fig. 5 uncertain, the telson being 

 absent)-. Greatest breadth of body nearly equal to the length of 

 eight segments, the relative proportion of length to breadth being 

 about the same as in the living genus j^ga. The abdominal segments 

 preceding the telson are, however, slightly longer in proportion, in 

 the fossil than in the recent form. 



A line divides the thoracic segments transversely into two parts, 

 the anterior being smooth and devoid of ornament, so as to admit of 

 the free movement of the preceding and overlapping segment upon 

 it, the posterior part being finely punctate and wrinkled ; where not 

 crushed, as in Fig. 3, the remains indicate that the terga were 

 strongly arched as in uS^ga ; the ej)imeral pieces are pointed and 

 curved backwards ; the fifth abdominal segment (that immediately 

 preceding the telson) has no epimera visible ; the telson is semi- 

 circular in outline, somewhat broader than long, and has a slightly 

 raised keel or ridge passing down its centre and terminating pos- 

 teriorly in a small spine ; the posterior margin is dentated ; the 

 lateral margin is ornamented along the border with a series of raised 

 plicce. None of the appendages are visible, save in Fig. 6, in which 

 the pair of foliaoeous plates attached to the terminal segment are 

 clearly to be seen occupying the same position as in Fig. 7. 



It is much to be hoped that further research may bring to light 

 more perfect remains of this interesting group, of which we know 

 so little in the fossil state, but which, from their abundance at the 

 present day, were in all probability well represented in past times. 



A form closely allied, if not identical with Palmga Carteri, occurs 

 in the Miocene of Turin, and has been described by Sismonda under 

 , the recent genus Sphcsroma as S. Gastaldi} ■ 



A comparison of the two recent genera, Sphceroma and ^^ga, with 

 the fossil species, confirms me in the conclusion that Palcega, as al- 

 ready pointed out, is more nearly allied to the latter than to any 

 other living genus of Isopods. 



In Sphceroma the epimeral pieces are less recurved ; the margin 

 of the telson is less circular, and it is destitute of the median ridge 



^ Sismonda, Eug. Descrizione dei Pesci e Crostacei fossili nel Piemonte Taf. iii. 

 fig. 10, in Mem. Accad. Torino, 2 Ser. Tom. 10. 1849. 



