686 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXII. 



MESOTHURIA PARVA (Theel). 



Plate LXXI, fig.s. 2, 2a-c. 



Mesothuria murrayi var. parra Theel, Challenger Holothurioidea, Pt. 2, 1886, 

 p. 187, pi. IX, fig. 2; pi. XVI, figa. 4, 5. 



General form and appearance almost exactly like that of preceding 

 species. Tentacles IS to 20. Pedicels of divers sizes scattered all 

 over body, those of ventrolateral ambulacra largest, there being one 

 or two irregular series especial!}' large. Median ventral pedicels 

 extremely small and scattered, often very few in number; those of 

 dorsal surface smaller than ventrolateral and fairly uniform as to size, 

 though some difference is discernible; pedicels, on the whole, rather 

 less numerous than in preceding species. Body wall rather thin. 

 Perisome roughened by spires of tables. Deposits: Tables composed 

 of a large disk with a central and numerous peripheral perforations, 

 and a spire of three rods with spinous apices; one cross beam. (For 

 shape of deposits see Plate LXXI, fig. 2.) No supporting rods to pedi- 

 cels, whose tables are much reduced in size. Color in alcohol either 

 3^ellowish white or purplish gray. Length about 95 mm. or less. 



Localities. — Forty specimens from following stations: 



List of stations. 



Label lost from one bottle of 20 specimens. 



The internal organization presents no marked points of difference 

 from that of the preceding species. The calcareous ring is of the same 

 general form; tentacle ampulla same. The ring canal and proximal 

 portion of the radial canals are large. Polian vesicle single. Madre- 

 poric canal, gonads, and respiratory tree practicalh' identical with those 

 of 31. inurrdy!. 



The tables differ from those of the preceding species in being much 

 crowded. They overlap markedly as in M. vaniom, whereas in 31. 

 inarrayi they arc not nearlj" so closely placed. Besides the difference 

 in form, which is more readil}' appreciated by a comparison of figures, 

 the disk in M. murrayi is frequently considerably larger. The disk 

 in M. jHtrva is more robust, with a greater number of perforations, 

 and the spire is lower and stouter, the crown ])eing more compact and 

 variable. Typical parva as figured b}^ Theel has no central perfo 

 ration in the crown, as is frequently the case with Tiawaiian exam- 

 ples. Diameter of disk averages about 0. 12 mm., height of spire about 

 0.085 mm. 



