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



Mai'etia (Spatangus), 



Maretia, Gray, 1855, Cat. Rec. Ech, 



Maretia alta (PI. XXXVII. figs. 1-4). 



Maretia alta, A. Agassiz, 1863, Proc. Ac. N. S. Phila., p. 360. 



As there are many excellent figures of Maretia jilanulata, I have figured Maretia alta 

 for the sake of facilitating comparison between these two recent species of the genus. The 

 specimens of this species collected by the Challenger show that it becomes considerably 

 larger than was previously known, one of the Challenger specimens measuring 35 mm. 

 ^n length. 



I could find no trace in the specimens examined of the rudimentary lateral fasciole 

 first seen by Duncan ^ in a fossil species of the genus, Maretia anomala. It, however, 

 occurs in the recent species of the genus, for among the many specimens of Maretia planu- 

 lata I found that some of them show a very distinct interrupted lateral fasciole, but far 

 less well marked than in Love7iia, where I have also detected a similar but a much better 

 defined lateral fasciole and one apparently uniformly present, which is not the case with 

 the rudimentary lateral fasciole of Maretia p)lanulata. 



Mai'etia carinata, Bolau,''* is evidently from its very characteristic description identical 

 with the species I briefly noticed in 1863 in the Proc. Phil. Acad., and subsequently 

 described more fully in the Revision, part 3, p. 569, 1873, as Maretia alta. 



The presence of only two to three large primary spines near the ambitus on the 

 abactinal surface gives this species (PI. XXXVII. figs. 1, 4) a very diff'erent aspect from 

 that of Maretia lylanulata, in which the whole of the abactinal surface above the ambitus 

 in the paired interambulacral areas is covered by many large primaries carrying long 

 curved spines often equalling in length half the length of the test, with a coarse miliary 

 intertubercular granulation, whde the miliary tuberculation of Maretia alta is close and fine, 

 the abactinal surface of the test, carrying only very short, slender miliary spines uniformly 

 distributed over the coronal plates. The bare ambulacral fields of the actinal surface are 

 also comparatively narrow in this species, the primary tuberculation of the actinal surface 

 extending nearer towards the actiuostome from the amljitus than in Maretia ijlanulata. 

 The difi"erence in coloration is also most striking, all the alcoholic specimens of Maretia 

 planulata are of a light straw colour, while those of Maretia alta are of a dark pinkish- 

 bufi" colour. 



Station 191. September 23, 1874. Lat. 5° 41' S., long. 134° 4' E. ; 800 fathoms ; 

 bottom temperature, 3*9° C. ; mud. 



Station 192. September 26, 1874. Lat. 5° 42' S., long. 132° 25' E. ; 129 fathoms; 

 mud. 



' Duncan, 1877, Quar. Journ. Geol. Soc, vol. xx.\iii. p. 52. 



^ Ur Heiniich Bolau Die Spatangiden des Hamburger Museums, Hamburg, 1873. 



