No. i.] MORPHOLOGY OF THE ACTINOZOA. 1 35 



prolifera (Fig. Ill) eight Edwardsia mesenteries (I-IV) are 

 present, perfectly developed ; in addition to these it has the 

 two Halcampa mesenteries (V-VI), which, however, have not yet 

 reached their perfect development, remaining in an immature 

 condition ; and finally a pair corresponding to the dorsal pair of 

 paired mesenteries of the Hexactiniae (VII) is developed. 



Amongst the Actiniaria collected by the United States Fish 

 Commission steamer " Albatross" during the winter of 1887-8, 

 I have found a form which is very interesting in this connection. 

 It was dredged in the neighborhood of the Santa Barbara Islands 

 off the coast of California, in fourteen fathoms. I propose to 

 name it Oractis diomcdeez. 



All the specimens are more or less contracted, and the exter- 

 nal ectoderm has been macerated away, leaving the mesogloea 

 exposed. It is consequently impossible to distinguish between 

 a capitulum, scapus, and physa which may have been present. 

 The base is rounded, and apparently was not adherent, and the 

 column is marked by twenty longitudinal furrows corresponding 

 to the insertion of as many mesenteries. On the portion corre- 

 sponding to the capitulum are ten prominent ridges or tubercles, 

 but I could not distinguish any perforations of the physal por- 

 tion of the column, such as Haddon (86) has described in 

 Peachia hastata. There are apparently ten simple, rather blunt- 

 pointed tentacles, with well-marked muscle-processes for the ec- 

 todermal muscles, the radial musculature of the disc being also 

 supported on similar processes. The stomatodaeum has only a 

 single siphonoglyphe, which is very deep with thick mesoglcea, 

 its ectodermal epithelium being destitute of gland-cells, and 

 resembling in appearance the epithelium of the lateral streaks 

 of the mesenterial filaments of the Hexactinians. On the gen- 

 eral surface of the stomatodaeum are six strong longitudinal 

 ridges, each one corresponding to the insertion of a mesentery. 

 I could find no trace of a conchula. 



The arrangement of the mesenteries may be seen from Fig. 2, 

 PL IX. There are two pairs of directive mesenteries (III and 

 IV), the ventral pairs (IV) being inserted into the bottom of 

 the siphonoglyphe. On each side of the ventral directives is a 

 small mesentery (V), imperfect, and without mesenterial fila- 

 ments and reproductive organs, having its longitudinal muscle 

 on the dorsal face. Next to it comes a perfect mesentery (I) 



