166 THE VOYAGE OF H.M.S. CHALLENGER. 



packed together (PI. XXIV. fig. 3). The lateral posterior ambulacra and the odd anabulacrum 

 are covered by minute miliary spines similar to the secondary spines of the abactinal surface. 



The subanal fasciole is broad, ^Dentagonal, pointed towards the actinal surface ; the anal 

 system is vertically elongate covered by a close granulation, the anal opening is near the 

 abactinal extremity (PL XXIV. fig. G), the intestine leading to this is short and slender 

 (PL XXIV. fig. 5). 



There is a very narrow thread-like peripetalous fasciole extending across the tip of the 

 lateral petals in the odd posterior interambulacrum and the lateral posterior interambu- 

 lacra, which becomes lost in the lateral anterior ambulacra (PL XXIV. figs. 1, 2). 



The abactinal system is compact ; the sutures between the genital plates are entirely 

 obliterated; there are four genital openings (PL XXIV. fig. 12) leading to four equally 

 developed genital glands, forming short grape-like clusters near the abactinal system (PL 

 XXIV. fig. 6). The madreporic body extends between the genital openings, and beyond 

 them in the posterior interambulacrum (PL XXIV. fig. 12). Seen from the interior of the 

 test, the calcareous canal forms a couple of loops for the passage of the genital ducts 

 (PL XXIV. fig. 7). The actinal ojoeningis pentagonal, pointed anteriorly, slightly labiate 

 posteriorly ; the actinal membrane is strengthened by small plates regularly arranged 

 (PL XXIV. fig. 11) ; the actinal tufted tentacles are comparatively small. 



The abactinal system of Homolampas closely resembles that of Paleopneustes ; it also 

 agrees with it in having the actinal surface eminently Spatangoid, while the abactinal 

 surface from the presence of rudimentary petals and simple ambulacral pores with com- 

 paratively large ambulacral plates, recalls the Pourtalesia group proper. The presence of 

 a well-defined subanal fasciole and of a lateral fasciole, as well as the presence of specially 

 developed primary tubercles, also places this genus closer to the normal Spatangoids. 

 The young of this genus, as in Homolampas fragilis, shows better than in such large 

 species as Homolampas fulva the aflinities of the genus to Pal(BOtropus ; from this genus 

 it mainly difiiers in the greater specialisation of the ambiUacra, and the presence of a peri- 

 petalous fasciole and a more labiate actinostome. 



In alcohol the test is of a light straw colour. 



Station 271. September 6, 1875. Lat. 0° 33' S., long. 151° 34' W. ; 2425 fathoms ; 

 bottom temperature, 1'0° C. ; globigerina ooze. 



Ho molampas fragilis. 



Lissonotiis fragilis, A. Agassiz, 1869, Bull. Mus. Comp. Zool., vol. i. 

 Homolampas fragilis, A. Agassiz, 1872, Eevis. Ecli., part 1, p. 137. 



Only a fragment of this species was collected by the Challenger, off the coast of 

 Northern Brazil. 



Station 122. September 10, 1873. Lat. 9° 5' S. to 9° 10' S., long. 34° 49' W. to 

 34° 53' W. ; 350, 120, 32, and 400 fathoms; mud. 



