14 BULLETIN OF THE 
and to overlap very little; the marginal plates are, as usual, of minute size. 
The scales bear numerous rounded granules, and, in addition, a very large cen- 
tral process or tubercle of conical form with rounded top. The valves and 
the marginal plates appear to be devoid of such tubercles. The largest tuber- 
cles attain a length of nearly 3 mm., and are placed one in each angle of the 
oval pentagonal shield. The anal pentagon has a rather prominent tubercle 
at each angle. The ventral sole is surrounded by a double row of pedicels, 
those in the exterior row perforating the margin of the body. Anteriorly, 
where the body is more contracted, the inner row appears to be double, but 
this evidently depends upon the contraction, The sole is strengthened by 
crowded large irregular plates of various size, perforated by numerous holes 
(the largest plates have as many as fifty holes or more) and provided with 
numerous rounded knobs; the ends of the knobs are sometimes united, 
thus constituting an irregular network on the exterior surface of the plates 
themselves. All the remaining forms are comparatively small, the smallest 
only 7 mm. long; as a rule, all the small specimens I have seen have more 
numerous and densely crowded tubercles, which generally resemble rather 
long spines, while the small rounded granules, on the contrary, are not so 
abundant, or may be even absent. 
Habitat. Off Sand Key (1877-78); depth 50 fathoms; one slightly con- 
tracted specimen. Barbados (1878-79), depth 103 fathoms, two small, con- 
tracted specimens; depth 84 to 125 fathoms, one small specimen; depth 73 
fathoms, three small specimens; depth 94 fathoms, two minute specimens 
7 mm. long. Barbados (Hassler Exp.), depth 100 fathoms; several small 
specimens. Dominica (1878-79), depth 118 fathoms; one specimen, 15 mm. 
long. Lat. 25° 33’ N., Lon. 84° 21’ W. (1877-78); depth 101 fathoms; one 
specimen, 15 mm. long, 13 mm. broad, 8 mm. high. (?) Lat. 23° 52’ N., 
Lon. 88° 5’ W.; depth 95 fathoms; two specimens which possibly do not 
belong to this species. 
Psolus Pourtalesi, n. sp. (?). 
Figure 6. 
All the specimens, which are of about the same size (80 mm. long, 20 mm. 
broad, and 6 mm. high at the mouth), are remarkable in being very depressed 
and flattened. With regard to the arrangement of the scales, and their size, 
they evidently resemble Psolus incertus of Théel and Psolus peroni of Bell, but 
they differ from these two species in several respects, especially in the shape 
of the body. As will be understood from the figures, Psolus Pourtalesi has 
numerous small, almost smooth scales, and is totally devoid of any oral and 
anal valves. The pedicels form a double row round the sole, those in the 
exterior row perforating the margin of the body. The odd ambulacrum is 
naked, or possesses a few pedicels in its anterior and posterior parts. The sole 
is strengthened with thinly scattered cruciform bodies, the arms of which often 
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