554 ME. J. CARTER ON THE 



is rather the largest of the segments. The epimera are somewhat 

 elevated in the central portion, bear several tubercles, and have 

 broadly rounded and flattened margins. Telson narrowing somewhat 

 towards the posterior border, which is very slightly rounded ; the 

 caudal endo- and exopodite are similar in size and form, each has 

 a strong longitudinal ridge ; the exopodite is not transversely 

 jointed, and bears a few tubercles. 



The limbs from the first to the fifth pair become gradually shorter 

 and more slender. The meropodite of the first pair is flattened, 

 smooth, and has tubercles on the posterior border ; the carpopodite 

 is about half the length of the meropodite and carries a few 

 tubercles : the propodite is about three times as long as the carpo- 

 podite ; in form it is subterete ; two rows of tubercles run along 

 the border and unite at the base of the process which represents the 

 fixed finger ; a similar row runs from each of the condyles which 

 serve for articulation with the dactylopodite and extends backwards 

 for the distal two thirds of the joint ; the space between these 

 rows of tubercles is roughly rugose. Dactylopodite straight, 

 slender, smooth, about half as long as the propodite ; the outer edge 

 is flattened, and has two longitudinal rows of minute punctures ; 

 sides flat, with similar rows of puncta ; dentary border very finely 

 serrate. As throughout the genus, all the limbs are monodactylous,. 

 the fixed finger being represented in the two anterior pairs by a 

 short acute process upon which the dactylopodite can be closed. 

 The propodite of the second pair is smooth, and has the widening of 

 the distal end typical of the genus ; in length it scarcely exceeds the 

 carpopodite, and it supports a dactylopodite, which has rows of 

 minute puncta and a minutely serrate dentary margin like the first 

 pair. 



Measurements. Length of cephalothorax from apex of rostrum 

 to posterior margin 15 millim. ; first pair of limbs — combined 

 length of the three proximal joints about 5 millim., meropodite 9, 

 carpopodite 5, propodite 16, dactylopodite 7. In some specimens 

 the propodite is relatively shorter ; this may be a sexual difl'erence. 



Oxford Clay, St. Ives. 



Coll. Mr. George, Northampton, Woodwardian Mus., and my 

 own. 



Specimens examined, numerous. 



This species is well figured and described by Herm. von Meyer 

 (Palseontographica, Bd. i. p. 144, tab. xix.), also by Quenstedt 

 (Wtirttemb. naturwiss. Jahresh. 1850, Tai. ii.). It occurs aubndantly 

 in the Oxford Clay of St. Ives, Huntingdonshire, but I am not 

 aware that its occurrence in any other British locality has been 

 previously recorded. By reason of the delicacy of the test the 

 specimens invariably occur in an imperfect state. Yon Meyer 

 states that it is found in several localities in Germany (Wurttem- 

 berg), frequently associated with Klytia (Eryma) MandelsloTii and a 

 species of Glyphea^ probably G. Munsteri. 



M. socialis is readily distinguishable from the other species of 

 the genus by its size and relative proportions ; it is most nearly 



