710 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxn. 



There are but two to four in the anterior half of the body, and a.s 

 noted above, the anterior fourth of body appears to lack them. About 

 seven or ei^ht of these midventral pedicels are situated within 10 or 

 16 mm. of anus and are somewhat difficult to separate from the lateral 

 pedicels. This will give an idea of how sparsely they are scattered 

 along rest of odd radius. No fold or collar is apparent on dorsal sur- 

 face above tentacles. Papillae are rather long here. Flank papillse 

 are all rather short. The longest ones are scattered along the inner- 

 most series of dorsum. 



Calcareous ring is not divided into separate pieces but forms a con- 

 tinuous ring. Radial and interradial portions are clearl}^ discernible, 

 however, the former having three prominent teeth anteriorly, and is 

 pierced I)}' a large hole. The exact form is best shown by fig. 2^, 

 Plate LXXVIII. The ring is very delicate and sometimes the lower 

 arms of interradial piece grow across the mouth of the posterior sinus, 

 forming an irregular hole. Just how constant this form is I am unable 

 to sa}'. Madreporic canal opens to exterior by several (at least five) 

 small tubules, just to the right of the genital papilla, which is about 

 12 mm. from anterior end of bod3\ Canal runs backward and upward 

 from ring canal, and the calcareous particles are much the same as in 

 P. oyioseleyi, possibly a trifle less twisted and interwoven. Polian 

 vesicle 20 mm. long, in left interradius of trivium. Gonad in a right 

 and a left tuft; tubules slender and thread-like, eight to ten times 

 dichotomously divided, extending to posterior extremity of body; not 

 bushy. Longitudinal muscle bands undivided, all five of about equal 

 width. 



In general perisome are large wheels very similar to those of P. 

 moseleyi^ with 10 to 14 spokes, most commonly 11. Their shape is 

 shown better by figures (Plate LXXVIII, fig. 2, 2^-, 2c) than by descrip- 

 tion. The diameter of these wheels is usually from 0.13 to 0.19 mm. 

 The crown, in center of nave, is made up of five or six arms, as is 

 sometimes the case in typical moseleyi. In ventral perisome wheels 

 are spaced, but in the dorsal they are more crowded. Small wheels 

 or wheel-like plates (fig. 2^) with three or four central and seven to 

 ten peripheral holes are especially abundant in walls of pedicels, but 

 are common also among large wheels. Their diameter is about 0.016 

 to 0.065 mm. Plates similar to TheePs fig. 8, Plate XXXII« are 

 found at tip of papilla?, and more or less deformed small wheels (fig. 

 26?) in addition, but no spicules like his fig. 9 are discoverable. No 

 plates like his fig. 7 were found, but as the dorsal processes of avail- 

 able material have been under the influence of weak acid the plates are 

 largel}^ imperfect. The disks of the pedicels are strengthened by 

 numerous perforated plates with wider and fewer meshes than TheeTs 

 fig. 11. There is but one layer of these plates, and in the smaller 



« Challenges Holothurioidoa, Pt. 1, 1882. 



