RAPHIODESMA. 165 



groups of the dermis. Those of E. lingua measuring 

 3~|-3 inch in length, while those of the similar groups 

 in R. fallaciosum were only 0-g-g- inch in length. A 

 striking differential character also exists in the biha- 

 mate, retentive spicula of the two species. In R. lingua 

 these organs are exceedingly numerous but very minuto 

 in the dermal membrane, while the same forms and 

 size are entirely absent in the dermis of R. fallaciosum, 

 and in the latter species, in lieu of these minute biha- 

 mate organs, there are a few comparatively large and 

 strong bihamate spicula sparsely distributed on the 

 membrane. The modes of structure and distribution 

 of the dermal fasciculi are the same in both species, 

 and the same observation holds good regarding the 

 structure and congregation of the inequi-anchorate 

 spicula of the rosette-like groups of the dermis ; they 

 are not composed exclusively of dentato-inequi-ancho- 

 rate forms ; a few of the bidentates are intermixed 

 with them. The number of spicula in one of these 

 groups is too numerous to be counted, and they are 

 so small as to require a power of about 300 linear to 

 render them distinct to the eye. With these closely 

 resembling points of structure in the two species a 

 close and critical examination and comparison of the 

 two species is essentially necessary for a correct discri- 

 mination of the two species, but the presence or absence 

 of the numerous minute bihamate spicula of the dermis 

 of R. lingua represented in Plate LXXVII, fig. 6, 

 vol. iii of this work, will, when a portion of the dermal 

 membrane of the specimen in course of examination 

 is mounted in Canada balsam, usually lead the observer 

 to a correct conclusion. The differences n the general 

 aspect of the two species may also assist in their dis- 



