88 PROCEEDINGS OF THE ACADEMY OF [1887. 



with his so-called "ovarian tubes," for we have been unable to find 

 any evidence that they pass into the calyx, or that they are longi- 

 tudinally perforate. 



We have been so fortunate as to obtain a large series of specimens 

 exhibiting the structure under consideration in more or less perfec- 

 tion in several species, and we are thereby enabled to present a 

 somewhat fuller description of its nature. AVe have observed it 

 in P. sulcatus in 2 specimens ; F. Godoni in 2 specimens ; P.pyriformis 

 in 4 specimens ; P. elegans in 19 S23ecimens ; P. cervinus in 3 speci- 

 mens ; and P. abbreviatus in 5 specimens, in all conditions of preserv- 

 ation. 



It consists in most of them often series of pieces that is five double 

 series, going out in salient angles toward the extremities of the inter- 

 radial pieces (deltoids) while in other species the series seem to be 

 composed of more than two ro\vs, and they are not so regularly ar- 

 ranged as in species with only two series. The pieces are located 

 at both sides of, and apparently Avithin, the so called spiracles. 

 They are, as clearly shown in perfect specimens, not plates but elon- 

 gate, tfi^jering spines, closely packed together, comparatively robust, 

 with a more or less obtusely quadrangular and sometimes, j^erhaps 

 triangular section, usually curving a little at the tips toward the 

 center. They vary in length, the outer ones being the shortest, 

 those toward the center the longest. We have been unable to dis- 

 cover anything like transverse sutures or longitudinal perforations, 

 and they probably consist of a single solid piece. Although limited 

 to the spiracles, their tips are generally drawn together so as to form 

 a kind of roof over the central opening, while if standing erect they 

 would leave a space in the middle. The spines apparently have no con- 

 nection whatever with the ambulacra ; the side pieces run out and dis- 

 appear at the spiracles, forming in fact their outer border, and only 

 the food grooves pass in between them to the peristome. Whether 

 the spines cover the spiracles directly, or rest upon independent 

 plates, we cannot say positively, but we are inclined to think that 

 the latter may be the case, and the plates bearing them are set in 

 around the inner margin of the spiracles, so as to cover the greater 

 })art of the opening, leaving perhaps a shallow channel passing 

 toAvard the center over the lip which we have described above. 



That the spines, or jilates bearing them, extended only over a 

 part of the so-called spiracles, is strongly indicated by the condition 

 of a very interesting specimen of the type of Pentremites symmetricus 

 Hall, from Chester, 111., in which it seems as if the whole pyra- 



