28 MR. T. BELL ON A NEW GENUS OF CRUSTACEA. 



straight from side to side ; the anterior and lateral margins form- 

 ing nearly a semicircle, the posterior margin straight ; the orbits 

 are deeply cut in the anterior margin of the carapace, looking 

 upwards ; the inferior margin wanting ; the oral apertul-e much 

 arched anteriorly ; the external footjaws with the third articula- 

 tion somewhat rhomboid, the fourth irregularly oval, and the palpi 

 tliree-jointed, inserted at its anterior and inner angle. Epistome 

 extremely small, transversely linear ; the external antennae placed 

 directly beneath the orbits, the basal joints partly filling them 

 beneath. The antennules folded transversely in large open fossae, 

 whicb are scarcely at all separated from each other, and are open 

 to the orbits, the eyes lying transversely; the peduncles short 

 and thick; the sternum is semicircular, the segments separated 

 by very deep grooves ; the abdomen very long and narrow, the 

 first and second joint transversely linear, the third and fourth 

 united and forming a triangle truncated anteriorly at the articu- 

 lation of the portion formed by the fifth and sixth joints united, 

 and wbicb with the seventh form a very narrow and linear piece 

 extending forwards to the posterior margin of the oral aperture ; 

 the first pair of legs robust, unequal (the right being the larger in 

 the only specimen at present observed) ; the hand in each as 

 broad as it is long ; that of the smaller conspicuously tuberculated, 

 that of the larger much less so ; the former with the fingers nearly 

 meeting throughout their length, those of the latter only at the 

 tips ; the second, third, and fourth pairs of legs are long, some- 

 what compressed, the third joint tuberculated on the under side, 

 the third pair the longest-; the fifth pair is reduced to a mere 

 rudiment, in the form of a minute tubercle inserted in a little 

 notch at the base of the first joint of the fourth pair, and scarcely 

 discernible by the naked eye. 



Observations. — The relation of this genus to the Pinnotheridae 

 is tolerably obvious, in the smallness of the antennae, the direction 

 and arrangement of the eyes, and particularly in the form of the 

 oral aperture, and of the external footjaws. I shall not, however, 

 enter upon the consideration of these relations, as I am about 

 shortly to offer to the Society a review and monograph of the 

 whole of this family. The most remarkable peculiarity in the 

 genus is the apparent absence of the fifth pair of legs, which can 

 only be discovered to exist at all by examination with the help of 

 a lens. In this respect I doubt not that the Eabrician genus 

 Hexapus, adopted and figured by De Haan, will be found to agree 

 with it, although it is very remarkable that the anomalous condi- 



