306 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 11 



that some of these individuals may represent the young of Semperothuria 

 languens, which must have quite similar spicules. However, as far as the 

 present material goes, none of these small individuals were taken where 

 adult specimens of S. languens occurred. Both species were preserved 

 in the bottle which contains Selenka's paratypes from Panama, but there 

 is no way of knowing whether this actually represents the one case in 

 which both were found in the same locality, or whether specimens from 

 different localities were lumped together under the general label "Pan- 



ama." 



7. Irenothuria n. gen. 



Diagnosis: Large species, 20 cm or more, cylindrical to bottle- 

 shaped, with 20 tentacles of moderate size and almost terminal in posi- 

 tion. Ventral feet cylindrical, large, arranged in irregular double rows; 

 dorsally the feet more papilliform and arranged in the same manner. 

 Calcareous ring delicate, low; one Polian vesicle and one free stone 

 canal with round head. Cuvierian organs present in some individuals. 



Spicules a crowded layer of tables. The largest tables with a disk 

 about 0.2 mm in diameter, with numerous holes and a tall spire with a 

 crossbeam near the base and four long smooth pillars turning outward 

 near the tip, each tapering to a point. Smaller tables also present, especi- 

 ally in the appendages — with shorter spire, often reduced to 1 to 4 knobs 

 or completely lacking. Ventral feet with large end plate; dorsal papillae 

 with no end plate but sometimes a few supporting rods with a few per- 

 forations near the ends. 



Type species: Irenothuria maccullochi n. sp. 



Remarks: The genus is monotypic and has been established to ac- 

 commodate one of the most striking shallow water forms brought home 

 by the Velero expeditions. The species was first collected by T. Morten- 

 sen in Panama in 1916 but no description was published, as it seemed 

 impossible that so large and unusual a form could be undescribed. 



Irenothuria maccullochi sp. nov. 

 PI. 4, figs. 1-4 



Diagnosis: As for the genus. 



Type: Allan Hancock Foundation. 



Type locality : Puerto Utria, Colombia, Velero III station 232-34. 



Distribution: According to our present knowledge, from Puerto 

 Utria, and Octavia Bay, Colombia; Bahia Honda, Panama; Puerto 

 Culebra, Costa Rica; to Ballenas Bay, Gulf of California. 



