DECAPOD CRUSTACEANS OF THE OXFORD CLAY. 553 



posteriorly), anterior portion with minute, round tubercles, two or 

 more diameters apart, on both dorsal and palmar surfaces, most 

 numerous near dorsal base of fixed finger; distal portion of outer 

 border flattened, margined by distinct ribs, which extend along the 

 fixed finger nearly to its apex ; the proximal moiety of these ribs 

 is delicately granulated ; the border of the hand corresponding to 

 the dactylopodite is rounded. Fingers longer than the hand, 

 flattened laterally, cultriform ; surfaces smooth, with a few seti- 

 gerous puncta ; outer edge flattened like that of the fixed finger, 

 and separated from both the palmar and dorsal surfaces by a distinct 

 ridge ; the distal three fourths of the dentary border of the fixed 

 finger bear 10 or 12 small subequal denticles ; the proximal fourth 

 is occupied by a single larger and longer denticle ; the dentary border 

 of the dactylopodite is trenchant, and divided into three nearly 

 equal portions by two slightly prominent denticles or angulations. 



I refer these elegant little chclas provisionally to the genus 

 Magila ; the specific name indicates the dissimilarity of the dentary 

 edge of the fingers. 



Length of chela 16 millim. ; width of hand 5 miUim. 



Oxford Clay, St. Ives. 



Coll. Mr. George, jSTorthampton ; my own. 



Specimens examined 2. 



Mecochirus socialis, Meyer, sp. 



Eumorphia socialis, Meyer, Palaeont. Bd. i. tab. x. figs. 2-10. 

 Mecochirus socialis, Oppel, Pal. Mitth. tab. xxii. figs. 2, 3. 



Length of carapace from apex of rostrum to posterior border 

 about twice and a half its greatest height ; test thin and fragile ; 

 surface closely and rather coarsely punctated ; puncta most numer- 

 ous near the ventral border of the branchial lobes, gradually disap- 

 pearing towards the dorsum; each in front of a minute tubercle. 

 A sharp, narrow, cervical sulcus, extending obliquely forwards and 

 downwards on each side from a point somewhat in front of the 

 middle of the dorsum towards the antcro -lateral angle, marks ofl" the 

 cex)halic portion, which occupies scarcely more than a fourth of the 

 total surface of the carapace; a slightly curved lateral cephalic ridge 

 runs from a small blunt spine on the frontal border nearly to the 

 cervical sulcus ; between this ridge and the antero-lateral border a 

 distinct cluster of tubercles occurs. Xone of the typical lobes of the 

 scapular region are definitely recognizable, except that a sharp 

 U-shaped sulcus, near the antero-inferior angle of the metabranchial, 

 indicates the lower extremity of the mesobranchial lobe ; in some 

 specimens the posterior arm of the U is prolonged obliquely back- 

 wards and upwards as a faint posterior mesobranchial sulcus. 



Rostrum simple, rather short, rapidly widening posteriorly and 

 longitudinally depressed in the mid-dorsal line. Abdomen about a 

 third longer than the cephalo thorax ; the first segment is the 

 shortest, and has in front a transverse ridge with a small lateral 

 tubercle ; a similar ridge crosses the posterior border ; the second 



