REPORT ON THE HOLOTHURIOIDEA. 61 



distinctly turned towards the ventral surface. The lateral ambulacra of the ventral 

 surface bearing very long and wide, cylindrical or conical, slightly retractile pedicels, 

 disposed either in a single or a double row along each side of that surface, and 

 sometimes provided with another series of extremely elongated, conical, non-retractile 

 processes placed externally and above the pedicels. The odd ambulacrum generally 

 naked, seldom with a few rudimentary pedicels or with a double row of rather large ones. 

 The dorsal surface with very long, elongated, conical, mostly non- retractile processes, 

 disposed in one or more rows all along each of its ambulacra. Calcareous deposits : 

 perforated plates, spicula, wheels, cruciform and dichotomously branched bodies. Cal- 

 careous ring composed of a rather fragile and imperfect net- work ; no distinct radial 

 or interradial pieces. 



The genera which are included under the head of this family seem in general to be 

 well defined. Deima differs from the others not only in having its calcareous skeleton 

 more fully developed and in the minute size of its tentacles and their capability of being 

 drawn within the body, but by the presence of a highly characteristic system of 

 canals, which is in communication with the water-vascular system, and is more fully 

 described in the anatomical part of this report. Oneirophanta bears the nearest re- 

 semblance to this genus from the shape of its calcareous bodies, but it differs from it 

 not only in the above noted peculiarities, but also in the number and position of its 

 processes and their degree of flexibility, and above all by the pedicels of its ventral 

 lateral ambidacra being arranged in a double row. 



As Orphnurgus is distinguished by its characteristic calcareous bodies, it keeps its 

 place as an independent genus. Lcetmogone, Ilyodcemon, and Pannychia constitute 

 a group by themselves, which is characterised by the perisoma containing wheels of 

 diverse dimensions. Lcetmogone carries only a single row of processes along each of the 

 dorsal ambulacra, and a single row of pedicels along each side of the ventral surface ; 

 while the two other genera are provided with numerous dorsal processes which are either 

 arranged in several more or less distinct rows along each ambulacrum or are scattered 

 irregularly over the lateral interambulacra. Like Lcetmogone, Ilyodcemon possesses 

 fifteen tentacles, and has its odd ambulacrum naked, but its lateral pedicels are disposed 

 in double rows. Pannychia, on the other hand, is provided with twenty tentacles, and 

 carries a single row of pedicels along each side and a double row of smaller ones along the 

 odd ambulacrum. There can be no doubt that these three genera are closely allied, and 

 this affinity is most striking between Ilyodcemon and Pannychia. As three species of 

 Lcetmogone have been discovered which have all the above-mentioned generic characters 

 in common, I feel convinced that this genus is well defined ; with regard to the 

 two others I take it for granted that the difference in the number of tentacles, and 

 above all in the arrangement of the pedicels, will justify their being placed as different 

 genera. 



