270 PEor. p. M. Duncan's ee vision op the 



subcentral; tlie anterior margin formed by broad ambulacral 

 plates ; peristomial interradial plates very narrow ; the labrum 

 narrow, long, projecting slightly ; a true amphisternum, which 

 is large and prominent. Phyllodian pedicels with a double 

 marginal series of circumferential filaments and a central five- 

 partite bulge. 



The ornamentation is small and miliary within tlie great groove; 

 small primary tubercles at the edge, larger beyond the fasciole, 

 and increasing to and over the margin of the test, crowded on 

 the sternum, usually several tubercles on a plate ; ambulacra 

 bare actinally. A peripetalous fasciole close to the sides of the 

 groove abactinally, crossing it in front and passing over the test 

 between the apical system and the posterior extremity, and 

 crossing the lateral ambulacra not far from the apical system, 

 and not interfering with the continuity of the pores. 



Periproct in the posterior truncation, circular, wilh numerous 

 concentric anal plates. Spines short, some larger and spathiform, 

 crowded on either side of the abactinal groove and upon the 

 sternum, those surrounding the periproct long, bent, and pointed ; 

 other spines smaller and curved. Some minute mushroom- 

 shaj)ed spines in the anterior groove. Large tentacles within the 

 fasciole and in the anterior ambulacra, with huge disks, fur- 

 nished with very numerous radiating, narrow, pointed supports 

 in a circle. 



Mecent. Sandwich Islands to Low Archipelago, Buenos Ayres 

 to Tristan da Cunha, Canaries ; 600-1900 to 2600 fathoms. 



The genus Aerope had a somewhat remarkable origin. The 

 ' Challenger ' Expedition started at the close of the year 1872, and 

 whilst in the Bay of Biscay, in that year, according to the Eeport 

 on the ' Challenger' Echini by A. Agassiz, 1881, p. 194, a species 

 of the genus was dredged, and a similar form was got from the 

 coast of Portugal in 1873. Nothing was heard of the extra- 

 ordinary form, and no notice was published of it, until Sir "Wyville 

 Thomson in 1877 described other specimens, which were dredged 

 in May 1873 between Bern-uda and 180 miles S.E. of Sandy Hook. 

 These specimens were described m Sir Wyville Thomson's unoffi- 

 cial work, ' Voyage of the Challenger,' Atlantic, i. p. 380, fig. 99 

 (1877). The description given is of a species, not of the genus. 



In 1875 the 'Valorous' sailed with the late Dr. J, Grwyn 

 Jeffreys and Mr. (now Dr.) Herbert Carpenter, and in a deep 



