THE APODOTJS HOLOTHURIANS 37 



Caudina albicans (Theel). 



There are 3 specimens from "Albatross" Station 2111, 35° 9' 50" N. and 

 74° 57' 40" W., 1,678 m. ; 1 from Station 2677, 32° 39' N. and 76° 50' 30" W., 

 860 m. ; and 1 from Station 2682, 39° 38' N. and 70° 22' W., 1,807 m. As no con- 

 necting links between this well-marked form and the preceding are known, it 

 is hard to see why albicans should not rank as a distinct siDeeies, instead of a 

 variety (armata) of arenata, as Theel ('86&) described it. The specimen 

 from Station 2682 is labeled "Trocliostoma albicans, det. A. E. Verrill." The 

 identification appears to be correct, but I am unable to find any satisfactory 

 ground upon which that sjiecies can be distinguished from Caudina arenata 

 armata; certainly the calcareous particles are identical. The name albicans 

 antedates armata. 



Caudina californica Ludwig. 



Besides the type specimen from "Albatross" Station 3434, Gulf of Cali- 

 fornia, 2,858 m., a larger molpadid, labeled " Southern Calif ornia probably, " 

 is in the collection, which is doubtfully referred to this species ; it is in poor 

 condition and the calcareous deposits are mostl^^ dissolved. There is also a 

 much smaller specimen, from Station 2838, otf Lower California, 85 m., which 

 seems to be a young californica. The numerous plates are smaller, more 

 svTTimetrical and with fewer perforations than in the type, but they are dis- 

 tinctly knobbed or provided with blunt spines. The differences seem to me 

 such as might be expected between the plates of a young and an old individual. 



Caudina planapertuea, sp. nov. 

 {plana, even, -j- apertura, openings; in reference to the smooth calcareous plates.) 



Plate IX, Figs. 6-8. 



Tentacles 15, each with 4 long digits. Calcareous ring not very stout, the 

 posterior prolongations of the radial pieces not very prominent and rather 

 pointed. Polian vessel single, long. Stone-canal single, lying in the dorsal 

 mesentery. Eesi3iratory trees long and delicate. Genital glands branched and 

 containing very large ova. Body elongated, tapering into the slender tail, 

 which is more than one-third of the total length. Calcareous particles in the 

 skin smooth, or slightly knobbed, plates perforated with many smooth holes. 

 Color gray, with minute light brown blotches, which are so numerous on the 

 back as to give a faint brown tinge to the dorsal side. Length, 67 mm., of 

 which the caudal portion is 27 ; diameter of body, 12 mm. ; of tail, 3. 



This species resembles C. arenata superficially, but is easily distinguished 

 by the very characteristic plates in the skin. It differs from C. californica in 

 having the plates smaller, much less numerous, and nearly or quite smooth. 



