James Carter — On a New Fossil Crustacean. 531 



tubercles being more developed than the marginal spines. This fact 

 is of interest as an indication that there is a difference in the morpho- 

 logical signification of these respective characters. 



Description. — Generic characters : — Carapace rather wider than long, 

 rostrum bifid, orbits opening forwards, orbital lobes well developed, 

 antero-lateral margin with acute spines, gastric regions obscurely 

 defined, branchial regions distinct, metabranchial lobe longitudinally 

 carinated. 



OritJiopsis Bonneyi (Carter). — Dorsal surface of carapace con- 

 siderably arched transversely, less eo in the direction of the mesial 

 ridge ; minutely granulated, and still more minutely punctated. 

 Antero-lateral margin rounded, rendered irregular by the unequal 

 prominence of the hepatic and anterior branchial lobes. A well- 

 developed, acute, slightly-curved marginal spine arises from the 

 hepatic and from each of the branchial lobes, that from the anterior 

 angle of the metabranchial being the larger ; a fifth — the stoutest of 

 the normal series — is constituted by the external orbital lobe. 

 Poster -lateral margin nearly straight, iticlining inwards so as to 

 render the posterior about equal to the orbito -frontal border. 

 Rostrum broad, widely bifid, divided into two stout, slightly- 

 diverging lobes. Orbits opening forwards, bordered above by two 

 distinct superciliary lobes, which are separated from each other by 

 a deep sinus and from the external orbital lobe by a sharp fissure ; 

 the external angle of orbit much produced, extending nearly as far 

 forwards as the rostral spines ; all the orbital spines are directed 

 horizontally forwards and outwards. Orbito^frontal region measur- 

 ing rather less than half the greatest width of the carapace. A 

 distinct sinuous sulcus separates the anterior gastric and the hepatic 

 from the branchial regions, but does not cross the dorsal carina, 

 ceasing abruptly at the point of junction af the meso- and meta- 

 gastric lobes ; a sulcus completely separates the posterior gastric 

 from the cardiac regions. Branchial regions sharply defined ; a 

 triangular epibranchial terminates about midway between the margin 

 and the median dorsal ridge, and is marked off from the meso- 

 branchial lobe by an undulating sulcus ; a similar and nearly 

 parallel groove — the inner half of which is obliquely crossed by a series 

 of elongated foveee — divides the meso- from the metabranchial lobes. 

 The metabranchial and cardiac lobes occupy the lai'ger posterior 

 half of the carapace ; a prominent, granulated, longitudinal ridge^ 

 slightly inflected in the middle, carinates each metabranchial lobe. 

 A median carina marks the anterior two-thirds of the carapace, 

 extending along the gastric and cardiac regions. There are a few 

 faintly-marked large tubercles, of which two occur on each proto- 

 gastric, one on the inner portion of the mesobranchial lobe, and 

 three or four on the median ridge ; those on the metabranchial 

 carina scarcely distinguishable. 



Length of carapace IJ in.; width (not measuring marginal 

 spines) 1| in. 



Localities. — Upper Greensand, Lyme Kegis, and Gault, Folkestone. 



