REPORT ON THE HOLOTHURIOIDEA. 53 



evenly rounded. The height decreases gradually backwards, consequently the posterior 

 extremity of the body has a rather flat aspect. The ventral surface is flat or slightly con- 

 vex, the dorsal, on the contrary, is extremely convex, especially anteriorly. The ends 

 of the tentacles are a little dilated, and are provided with processes of which those 

 round the edge appear to be largest. The pedicels are arranged all along each side 

 of the ventral surface, the first pair arising a little behind the tentacles. The first 

 five pairs are separated from each other by certain distances and disposed along 

 the anterior four-fifths of the body ; the distance between the different pairs decreases 

 gradually backwards. The posterior six pairs of pedicels are, on the contrary, closely 

 crowded side by side around the posterior fifth part of the ventral surface, several of the 

 middle ones being very small ; they are webbed together by an extension of the skin, 

 leaving only their ends free. The dorsal appendages are exactly like those of the 

 preceding species. The broad, transverse and almost flat lobe, situated about 10 mm. 

 behind the tentacles, reaches an unimportant height, only about 10 mm., the projections 

 included; its two middle projections present a conical form and attain a considerable 

 size in comparison with the other two, which are almost imperceptible. Immediately 

 behind this lobe two very small papilla-like eminences are to be observed, one on each 

 ambulacrum, and behind those arises another pair ; sometimes both of the pairs seem 

 to be wanting. The perisoma is glassy, thin, and transparent, that of the ventral 

 surface possessing a higher degree of pliability and less roughness than that of the dorsal, 

 which to the naked eye appears to be closely covered with minute spines. There 

 exists a remarkable difference between the calcareous deposits of the upper and under 

 surfaces of the body ; those in the dorsal perisoma (PI. XXXIV. fig. 13), are very closely 

 crowded, and consist of four strongly arcuated and finely spinose arms, directed inwards and 

 measuring about 0"28 mm. in length or more, and of one, two, or three straight, slightly 

 spinose processes, which being directed outwards, cause the great roughness of the 

 integument. The arms either run out from a common central point or from the ends 

 of a more or less elongated, rod-like central part. These calcareous deposits bear the 

 strongest resemblance to those of Peniagone vitrea. The deposits of the ventral perisoma 

 (PI. XXXIV. fig. 12) are slightly smaller and more thinly scattered, and resemble the 

 former ones, but differ by having their arms not so obviously curved and only measuring 

 about - 14 mm. in length or less, each arm carrying close to the elongated central 

 part a short spinose process. The deposits of the oral disk resemble those of the 

 preceding species. The tentacles contain a number of larger or smaller, often strongly 

 arcuated, spicula, with the ends more or less spinose, and among those are to be found 

 three- or four-armed irregular bodies. The ends of the pedicels are provided with a 

 smaller number of arcuated, unbranched spicula, mingled with some four-armed bodies 

 without processes. The five pieces of the calcareous ring are separated from each other 

 as is the case in the preceding species ; it is possible that they might meet each other, 



