ALCYONAEIA WHITELEGGE. 313 



light under the microscope it presents an appearance like the axis 

 of Plexaura flavida.* 



The polyps are alternate or often in pairs on opposite sides, 

 especially at the summits of the slender twigs, they occur at 

 intervals of from '5 to ! mm. they are *5 to '6 mm. in diameter, 

 and from - 7 to *8 in height, in shape they are roundly conical, on 

 the stem and branches, whilst the terminal ones are usually 

 cylindrical. 



The ccenenchyma is very thin, the branches are encircled by a 

 single layer of quadriradiate spicules, the rays are frequently at 

 right angles to each other, they are bent down in such a manner 

 as to embrace the stem, the upper central ray is produced and 

 projects through the ccenenchyma, giving the stem and branches 

 a spiny outline. 



The external spicules of the verrucse are triradiate, the upper 

 ray being long and spine-like, and project through the tissues, at 

 angles varying from the horizontal to the perpendicular, the lower 

 rays are imbedded in the ccenenchyma and are very variable in 

 shape, in some cases they are simple tuberculated spines, in others 

 the spines are distinct but they are connected by a perforate plate, 

 or the spines may give place to a many rayed perforate plate, 

 beset with minutely beaded tubercles. 



The summits of the verrucse are surmounted by a series of long 

 acute spicules, resembling those of the walls but having the pro- 

 jecting ray longer and the imbedded portion more strongly but 

 irregularly developed. 



The tentacles have at their bases externally a few irregular 

 curved spindles, with a minutely granular and tuberculated 

 surface, on the convex side near their free ends, they are usually 

 provided with three or four teeth-like processes ; similar but 

 smaller spicules exist in the tentacles, the denticles often project- 

 ing at their apices. 



(1) The quadriradiate spicules of the ccenenchyma have acute 

 points and a few blunt spines, they measure in their widest 

 diameter -15 by -2 mm., they are from -1 to -15 mm. in height, 

 the rays are from -07 to '1 mm. in length and '03 mm. in diameter, 

 the apical spines are from '03 to ! mm. in length. 



(2.) The triradiate spicules of the verrucse measure in their 

 widest diameter from -15 to '35 mm., their height is from -15 to 

 3 mm., the free acute ray is from *1 to '2 mm. in length and 

 05 mm. in diameter. 



(3.) The apical spicules of the verrucse are from -3 to '5 mm. 

 in height, and from '2 to -4 mm. wide at the base, the free spine 

 being -15 to '25 mm. in length and '05 mm. in diameter. 



* Kolliker Icones Hist., ii., 1866, pi. xii., fig. 5. 



