96 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



Ossicles. The calcareous segments or plates of which the crinoid skeleton is com- 

 posed; the term is not employed to include the smaller dermal plates and 

 spicules. 



Outer cirrals. See Distal cirrals. 



Overlapping spines. Spines developed in the median or submedian line of the 

 brachials which extend obliquely forward, thus overlapping the bases of the 

 succeeding brachials (see figs. 35, p. 73, 46, p. 81, 94 (outer part of arms), 

 p. 155, and 99, p. 160). 



Ovoid bodies. Dark, more or less spherical bodies seen in the substance of the 

 pinnules of the ungrooved posterior arms of certain comasterids; these are 

 sometimes known as sensory bodies. 



P. 



Pair. Of pinnules; two immediately succeeding pinnules, each of which is on the 



opposite side of the arm from the other. 



This term is not used except in reference to the proximal pinnules, of 



which the pairs are P t and P a , P 2 and P 6 , P 3 and P c , etc. (see fig. 6, p. 63). 



Ungrooved arms such as are found on the posterior radii of certain of the 



Comasteridse, end in a pah* of pinnules, both of these pinnules arising from a 



single axillary brachial (see fig. 47, p. 81, and p. 110). 



Of arms; see Arm pair. 



Paired dorsal spines. Dorsal spines which occur, two on each cirral, side by side in 

 a line at right angles to the longitudinal axis of the cirrus (see figs. 345-348, 



p. 289, 349, 350, p. 291, and pp. 284-285). 

 Palmar axillary (IIIBr a:c ). The third postradial axillary; the terminal ossicle of 



the palmar (IIIBr) series. 

 Palmar pinnules (P P ). Pinnules developed on the ossicles of the IIIBr (palmar) 



series. 

 Palmars (IIIBr). The ossicles of the third division series; they are two, three or 



four in number, and, so far as known, always terminate in an axillary which 



may bear either two undivided arms or two post-palmar (IVBr) series. 

 Parambulacral. Bordering the ambulacral grooves. 

 Partial regeneration. Of the cirri (see Regeneration, B2). 

 Pentacrini. Pentagonal or stellate coluninals, such as are found in the columns 



of the pentacrinites; this term is usually applied to these columnars only when 



found fossil. 

 Pentacrinoid. The stalked larva of a comatulid; this term is commonly restricted 



so as to refer to the period between the formation of the arms and the loss of 



the stem (see fig. 533, pi. 3). 

 Pentacrinoid larva. See Pentacrinoid. 



Pentagonal base. The five radials in situ, including within them the rosette. 

 Pentamerous symmetry. See Symmetry and Axis. 

 Penultimate segment. Of the cirri, the segment which bears the terminal claw on 



its distal end, and the opposing spine on its dorsal side (see figs. 314, 315, 



317, 318, p. 273, and pp. 278-280). 



