1889.] NATURAL SCIENCES OF PHILADELPHIA. 109 



the rest of the stomatodseum. Its mesogloea is much thickened, and 

 is devoid of processes upon its ectodermal surface, being thus strongly 

 contrasted with that of the stomatodseum. In its histology the 

 ectoderm of the groove also differs from that of the general stomato- 

 dseum, the glandular cells being evidently fewer in number, but the 

 preservation of the specimens was not sufficiently perfect to permit 

 the details to be made out. 



There are altogether twenty-four pairs of mesenteries, twelve of 

 which are perfect. The six primary pairs are united with the stom- 

 atodseum to a greater extent than are the six secondaries, and the 

 two pairs of directives have a much more extensive union than any 

 of the other primary mesenteries, owing to the great prolongation 

 of the gonidial grooves. The longitudinal muscle processes form a 

 strongly projecting though rather narrow band, the edges of which 

 are sharply defined, the processes being of equal length throughout 

 the muscular area and diminishing abruptly towards the sides. The 

 mesogloea of the portion of the mesenteries external to the muscle 

 bands is rather thick, and there is a strong parieto-basilar muscle. 

 Apparently only the mesenteries of the third cycle, i. e. the imper- 

 fect mesenteries, are gonophoric, but my preparations do not allow 

 of certainty on this point. 



A few remarks are called for concerning the relationships of this 

 species. I was at first tempted to identify it with 0. formosa 1 but 

 further consideration led me to separate it as a new species. The 

 fronds differ markedly from those of other species of Oalactis. In 

 these they have been described as being " chicoraces," a term which 

 cannot be applied to the fronds of O.fascicukda. In it they consist 

 of bunches of finger or club-shaped hollow processes, the various 

 processes of each bunch being united by their base but distinct 

 above. This arrangement suggested the specific term which I have 

 employed, and I think is of sufficient importance to warrant the forma- 

 tion of a new species. It was a question whether a new genus should 

 be instituted as VerrilP has done in the case of Lophactis omata, but 

 there is such close agreement with the Bahaman 0. flosculifera as 

 regards the internal structure, the number of perfect mesenteries, 

 and the distribution upon the mesenteries of the reproductive 



1 Duchassaing and Michelotli — Mem. Reale Accademia di Torino. 2nd Ser. 

 xix, 1860 and xxiii, 1866. 



2 Verrill A. E.— Trans. Conn. Acad. Vol. i, 1868. 



