FROM TIJE INLAND SEA OF JAPAN. 443 



angles are not sharp and reach almost as far forward as the front. The antero-lateral 

 margin is not shorter than the postero-lateral. The slightly convex outer edge of the 

 flattened, extraorhital tooth is heset with three or four subacute granules, but its upper 

 surface is smooth. Tlie granules of the extraorhital tooth arc followed, iu the larger 

 female, by six or seven sphiiform, sharp teeth, of which the last is much smaller than the 

 rest, which are subequal and nearly of the same size ; in the other specimen there are 

 eight spines on the left and seven on the right side, those of the left being a little more 

 unequal. These teeth or spines are smooth and glabrous. The lateral spines of Pot. 

 {Parajjotamo)i) spinesceiis are more acuminate and there are only five or six on each 

 side. The rounded postero-lateral margins are smooth, converge less stronc/li/ back- 

 ward than those of Pot. spinescens, and run almost parallel. The posterior margin of 

 the carapace is Just half as broad as the latter is long and appears thus comparatively 

 broader than in Pot. spinescens; it is also much more concave than in that species. 



The orbits are, in the larger specimen, a little more than half as broad as the frontal 

 border ; as they have exactly the same measurements in both females, they appear 

 in the younger specimen comparatively larger. They are diiferently formed than iu 

 Pot. spinescens. The orbits are more regularly oval, their outer margin being more 

 regularly curved (PI. 33. fig. 60) ; the lower margin is more distinctly crenidate than 

 the upper, and, as in Pot. [Parapotamon) spinescens, the inner angle is not produced at 

 all, but there is an internal suborbital lobe, inserted between the inner angle and the 

 basal joint of the outer antennae. In Pot. spinescens this lobe is semi-elliptical, obtuse, 

 its outer surface is concave, and it reaches beyond the middle of the orbital hiatus ; in 

 Pot. endymion the lobe is subacute and considerably smaller, its length being only one- 

 third of the width of the orbital hiatus. The basal joint of the outer antennse has also a 

 different form in the two species ; in Pol. spinescens it is just as long as broad, it does not 

 reach the front, and its outer surface is slightly convex ; in this new species, however, 

 the basal joint is longer than broad, its outer surface is quite flat, and it narrows 

 distinctly towards the front, which it attains (fig. 61). 



The subhepatic and subbranchial regions are smooth, but the ptei-ygostomian area is 

 somewhat granular on its outer half. 



The epistome, which is smooth, is a little longer in proportion to its breadth than in 

 Pot. spinescens. In that species the granulated posterior margin is not prominent in 

 the middle, but the granulated ridge, which extends from the middle backward into the 

 ])uccal cavity, is very promiuent. In Pot. endymion we observe just the contrary, the 

 granulated posterior margin of the epistome forms a prominent tooth in the naiddle line, 

 liut the ridge into the buccal cavity is hardly distinguishable. 



The external maxillipeds (fig. 62) are characteristic. Tlie longitudinal groove on tho 

 ischium, which in Pot. spinescens is well-marked, is Avanting, or, at the utmost, a faint 

 trace of it is discernible; this joint is punctate, the puncta are a little larger and more 

 crowded near the inner border. The merus-joint, wliich in Pot. spinescens is once and 

 a half as broad as long, api)ears in Pot. endymion hardly broader than long; in the 

 larger female it is 3 mm. long, but only 2*4 mm. broad ; it is quadrangular, the 

 straight inner border and the equally long antero-intcrnal being much shorter than the 



SECOND SERIES. — ZOOLOGY, VOL. IX. 63 



