20 FOSSIL MALACOSTRACOUS CRUSTACEA. 



Necrocarcinus Bechei, sp., Bcslongchamps. Plate IV, figs. 4 — 8. 



Testa suboibiculari, ruodicc convexa, tuberculis quindecem instructa, rostro inermo. 



Orithyia Bechei, Beslongch. (1836). Mem. Soc. Lin. Norm., v, p. 40, t. i, figs. 7 — 9. 

 Arcania Bucklandii, Manlell (1844). Med. Cr., p. 534 ; Geol. Suss., t. xxix, figs. 



7, 8, 14 ; S.E. Eug., p. 159, fig. 3. 

 NoTOPOCOKYSTES Bechei, Morris. Cat., p. HI. 



Bescr. The carapace in this species is of equal length and breadth, moderately con- 

 vex, the height from the plane of the lateral margin being not more than one fourth of the 

 diameter ; the nuchal furrow deep and broad ; the rostrum triangular, hollowed in the 

 centre, and without teeth at the sides ; the regions and lobes raised ; there arc, in all, fifteen 

 large tubercles on the carapace, besides a few small ones on the latero-anterior margin, and 

 an obsolete one immediately behind the rostrum; of these there are two on each proto- 

 gastric lobe, one on the metagastric, one on the urogastric, one on the cardiac region, 

 one on each epibranchial lobe, one on each mesobranchial, and two on each metabranchial. 

 The posterior margin is hollowed, and immediately anterior to its raised edge is a rather 

 deep depression. The orbits are nearly round, and there are two distinct fissiu'cs on the 

 upper margin, with a small tooth between them. The oral aperture is about as broad as 

 it is long, with the edges slightly curved. 



Of this species I have never seen the footjaws, the abdomen, or the legs, nor even any 

 portion of these parts, excepting a hand, figured in Plate V, fig. 3, which indicates a 

 minutely granulated surface and a short, rounded, and robust form ; the moveable finger 

 bent down to meet the other, which is merely a small pointed process. 



Obs. This species is not at all unfrequent in the Gault of Folkestone and in the upper 

 Greensand in the neighbourhood of Cambridge, but I have not seen it from any other 

 locality. The specimens from the two beds above named differ considerably in colour and 

 surface, those from the Greensand being generally much more injured, both from abrasion 

 and fracture, than the others. I have also observed that the single small tubercle at the base 

 of the rostrum is ordinarily more conspicuous in the Cambridge than in the Folkestone spe- 

 cimens, being in the latter often scarcely discernible. These circumstances, however, are 

 not suificient to constitute specific distinctions. 



Necrocarcinus Woodwardii, BcU. Plate IV, figs. 1 — 3. 



Testil orbicular!, subglobosa, tuberculis circa viginti instructa, rostro utriuque ad basin 

 minute unidentato. 



Dencr. The carapace in the present species is nearly orbicular ; it is much more elevated 

 than in the former, and in the young state nearly semiglobose ; the regions separately are 



