REPORT ON THE ISOPODA. 13 



pair of antennae, which is composed of a considerably greater number of joints than in 

 that species ; in the form of the first pair of ambulatory limbs, the antipenultimate joint 

 being prolonged beyond the point of articulation of the succeeding joint in Stenetrium 

 haswelli, and not so prolonged in Stenetrium fractum. 



From Stenetrium armatum also in the greater length of the flagellum of the 

 antennules, which are stated by Haswell to possess from eight to twelve joints only 

 in that species ; in that species also the penultimate joint of the cheliform appen- 

 dages " is defined by a long acute spine, and armed in addition with a bifid denticle 

 situated about its middle;" there appears to be no trace of this latter in Stenetrium 

 haswelli. In his description of Stenetrium armatum Haswell makes no mention of a 

 molar process to the mandible, which is certainly present in Stenetrium haswelli. 



From Stenetrium inerme, Haswell's second species, the present is easily to be distin- 

 guished by the form of the eyes, which have the narrow oblong form characteristic of the 

 genus ; in Stenetrium inerme the eyes are said to be rounded ; in the antennules of 

 Stenetrium inerme the third joint of the peduncle is scarcely distinguishable from the 

 fiagellum ; in Stenetrium haswelli there is no possibility of confounding the third joint of 

 the peduncle with the succeeding flagellum, the joints of which are much shorter as well 

 as narrower. 



Station 320, off the Rio de la Plata, February 14, 1876; lat. 37° 17' S., long. 

 53° 52' W.; 600 fathoms ; bottom temperature, 37°'2 F.; green sand. 



Ianthe, Bovallius. 



lanthe, Bovallius, Bihang til Svensk. Vetensk. Akad., Bd. vi., No. 4. 



Ianthe, Studer, Isopoden gesammelt, &c, Abhandl. d. k. Akad. d. "Wiss. Berlin, 1883, p. 10 (of memoir). 



This genus was founded by Bovallius to include a small species of Isopocl from the 

 Arctic Ocean, which with the same general shape as Janira, differs from it in the following 

 particulars : — in the great convexity of the body, in the small and distant eyes, the want 

 of an articulated scale on the peduncles of the antennas, and in the presence of a well 

 developed mandibular palp. In other respects the species Ianthe speciosa agrees very 

 closely with Janira, the uropoda are large and biramose as in that genus, and both pairs 

 .of antennary organs are furnished with a long flagellum. These last named particulars, 

 as also the modification of the first pair of thoracic limbs into a prehensile appendage, 

 serve to separate lanthe from Jsera. The general aspect of lanthe speciosa, judging 

 from Bovallius's beautiful illustration, is very unlike the typical form of the genua 

 Janira, as represented in such species as Janira maculosa, Janira hreviremis, Sars, 

 and others ; but Harger has recently described and figured a new species clearly refer- 

 able to the genus Janira, which bears a very striking resemblance to Ianthe speciosa. 

 It has the same double row of spines down the back, a long rostrum, and in both species 



