238 J- Playfair McMuhrich, 



velopment in diiFerent individuals, in some being very narrow and 

 destitnte of muscle pennons and mesenterial filaments, wliile in others 

 tliey are broader and possess these structures. All the mesenteries 

 may be fertile, witli the possible exception of the directives. The 

 longitudinal muscles of the first three cycles are well developed, 

 oecupying about one-half the muscle-bearing snrface of the mesentery, 

 The proeesses vary somewhat in height in different individuals, 

 Fig. 46 representing an average condition. The parieto-basilar forms 

 a distinct fold, often more marked than that shown in Fig. 46 and 

 the basilar mnscles are well developed (Fig. 47). 



The diiferenees in color in this form and Lesson's A. oceUata 

 seem to be explainable by the fact that the coloration is the re- 

 snltant of a diffuse ectodermal pigment and a granulär endodermal 

 one which varies in the amount of its development. It may be 

 noted that there is a probability that Lesson's A. papulosa is 

 identical with his A. ocellafa but there is too much uncertainty about 

 this as yet to Warrant the combination of the two under the term 

 A. papulosa. 



Family ParacUdce R. Heetwig, 1882. 



Actininae with an adherent base; sphincter mesogloeal; mesenteries 

 arranged in several cycles, of which usually more than one is perfect ; 

 longitudinal muscles of the mesenteries usually diffuse, parieto-basilars 

 and basilars unequally developed; no acontia. 



Genus JParactis Milne Edwakds et Haime, 1882. 



Paradidae with thin and smooth column wall; tentacles of 

 moderate length and of uniform thickness throughout; margin not 

 lobed; the individual mesenteries of each pair equally developed. 



The genus Paractis possesses a somewhat doubtful Standing if the 

 first species mentioned under a new genus is to be recognized as its type. 

 The genus was established by Milne Edwards & Haime in 1852 

 and the first species mentioned under it was P. impatiens (CouTHOuy), 

 a form which I find in the present collection and which proves to 

 be a Sagartiid. The precise definition given to the family Paractidce 

 by R. Heetwig removes, however, any danger of confusion as to tlie 

 forms which should be assigned to it and it seems probable that had 

 Milne Edwards known of the possession of acontia by P. im- 

 patiens he would not have included it in the new genus. The 



