248 



PB0F. A. C. HADDOtf ON" TWO SPECIES OF 



of which was devoted to the microtome, the other two are 

 uninjured. 



Except where otherwise stated, the following descriptions 

 apply to the specimens as they appear after preservation in 

 alcohol, and in a very contracted condition. In my definitions I 

 have largely followed the method of procedure advocated by 

 Professor E. Hertwig. 



Mykiactis *, n. gen. 



Hexactiniae [as defined by E. Hertwig] with slightly developed 

 endodermal muscles in the upper portion of the body-wall, and 

 strong mesenteric retractor muscles ; a large number of mode- 

 rately long, slightly contractile, subequal, polycyclic tentacles, 

 the marginal row being papilliform ; numerous complete mesen- 

 teries [" septa " of Hertwig]; reproductive organs present on 

 all the mesenteries ; wall, smooth below, provided with suckers 

 above. 



Mtutactis tfbicola f, n. sp. (Plate XIX.) 



Form. Cylindrical ; base not expanded, thrown into a number 

 of radiating ridges, with concentric rugosities, thus giving it a 

 reticulate appearance ; scapus thin-w r alled, with the mesenteries 

 shining through in the less contracted portions, transversely 

 wrinkled ; the closeness of the folds in the most contracted 

 portion of the body it gives a satin-like lustre ; capitulum 

 non-retractile, transversely folded, but not nearly to the same 

 extent as the scapus, provided with numerous suckers ; the 

 latter are most developed above, and become less prominent 

 below ; at the region where the capitulum imperceptibly passes 

 into the scapus the suckers are very irregular in size and dispo- 

 sition, and give a perforated appearance to the body-wall. Margin 

 of disk thrown into folds. Tentacles moderately long, conical, 

 fairly uniform in size in eight or nine rows, over four hundred in 

 number, not counting the marginal row. Gonidial furrows 

 prominent. 



Colour. " Disk and tentacles pale green. My impression is 

 that they were barred or spotted." [J. A., IIS.'] Uniform grey, 

 in spirit. Tho green colour in the living animal is almost cer- 

 tainly due to the presence of zooxanthella), which occur in enor- 



HvpUn innumerable, uteris a ray. 



t So named from its habit. 



