A. E. Verrill — New Actinians. 209 



Paractis nivea (Less.). Figure 16, page 146. 



Actinia nivea Lesson, Yoy. Coquille, p. 81, pi. iii, fig. 8, 1832. 



Sagartia nivea Verrill. Trans. Conn. Acad., i, p. 485, 1869 (non Duerden). 



Aiptasia nivea Andres, op. cit., p. 175, 1884. 



The wall in most parts of the column is very thin, but 

 strong and parchment-like, often with smooth satin-like ap- 

 pearance, and when seen with a lens it may appear somewhat 

 fibrous transversely ; it shows about 48 mesenterial lines. In 

 contraction it is variously, but rather closely and deeply, 

 transversely wrinkled, showing that it is a much elongated 

 species when in full expansion, The sphincter muscle is 

 rather broad and diffuse, without a very definite outline. The 

 mesogloea is thickened near the summit so as to form a fold in 

 contraction ; another fold often occurs lower down, when 

 strongly contracted, the upper part being somewhat invagi- 

 nated into the lower. In these examples there may appear to 

 be a second sphincter, due to the longitudinal contraction. 



The perfect mesenteries are usually in 12 pairs, but vary 

 from 12 to 16, and rarely 21 pairs, all of which appear to bear 

 gonads. A variable number of small mesenteries occur be- 

 tween the perfect ones; usually those of the third cycle are 

 well developed and bear gonads, but those of the fourth cycle are 

 very rudimentary and do not bear gonads; small rudiments of 

 the fifth cycle may also occur. The longitudinal muscles of 

 the perfect mesenteries are not very thick, but cover most of 

 their breadth. 



Tentacles are very numerous and may be entirely infolded 

 and concealed; in the larger examples there are over 120; 

 they are closely crowded in four or five rows ; even in alcohol 

 they are rather long and slender with acute tips ; the outer 

 ones are much smaller than the inner. In some alcoholic 

 specimens, preserved for thirty years, the tentacles, when they 

 have been protected by retraction, still retain a reddish brown 

 tint, but others are pure white. The tentacles in a large num- 

 ber are fully exposed. Probably the color is variable in life. 



The larger specimens are 15 to 18 mm in diameter ; some are 

 25 to 30 mm long, with a diameter of 8 to 10 mm . 



Callao, Peru, on the bottom of an old vessel that had been 

 more than a year in that port. They were mostly living in 

 the interstices of large clusters of Discina Icevis. 



This species looks like a Sagartia, but no acontia were found 

 in numerous specimens dissected, hence I refer it to Paractis. 



Subgenus Archactis, nov. Type A. perdix. 



Body nearly smooth in expansion, broad, usually cylindrical ; 

 base broad, muscular ; margin without distinct fold or thicken- 

 ing, in expansion ; disk broad, often undulated ; tentacles 



