Micksonella, a New Gorgcnellid Genus. Bij J, J. Simpson. I 35j 



was first described and figured by KiiUiker in his Icones Histio- 

 logies, p. 140, taf. xviii. fig. 46. In the Revision of the Juncellid- 

 group of the Gorgonellidje several figures of this type of spicules are 

 given (fig. 4, a-g). 



Tiie general form approaches that of the well-known " Indian 

 club ;" there is a distinct smooth median part or liandle, which is 

 surmounted by a few spines. The club-part also Ijcars spines, and 

 the most important characteristic is the fact that these species are 

 all directed away from the shaft, and do not arise perpenilicularly. 



Some doubt seems to have arisen since tlie time of Kolliker as 

 to the exact nature of the " club," and this dubiety accounts for 

 the original inclusion of the species sjnralis in the genus Juncdla. 

 Hickson (op. cit.) describes a form of s]iicules as a club (pi. viii. 

 fig. 8), but it is a club essentially different from Kdlliker's type. 



The spiculation as a whole is quite unlike that of any species of 

 Juncdla (op. cit., figs. 14, 23, and 26), so that it is imjjossible to 

 refer the present specimens to that genus. They are even further 

 removed from Scirpearia and Nicdla, so that it seems necessary to 

 form a new genus to include them. 



Diagnosis of Hidcsondla , g . n. 



Colony simple, flagelliform, and generally twisted in a mure or 

 less open spiral at least in the ohler colonies. Tlieaxis consists of 

 concentric lamina' which are comi>osed of a horny substance im- 

 pregnated with some form of calcareous matter. It is generally 

 hard, and the surface is marked by longitudinal ridges and furrows. 



The coenenchyma is extremely thin and densely s])iculose ; it 

 is very brittle, especially when dry. The polyps are disposed in a 

 broad longitudinal liand ; this leaves a narrow bare strip which 

 traverses the whole length of the colony. The verrucas are not 

 retractile into the coenenchyma, and are elongated, slender and 

 slightly club-shaped in the upper portion ; they are covered with 

 minute spicules, which appear like overlapjiing scales; the spicules 

 on the aboral surface of the tentacles form a sort of pseudo- 

 operculum to the partially retracted anthocodia. 



The spicules vary in th(^ dilferent species, but the following 

 are the cluef types: — (1) Irregularly warted spindles; (2) Hat, 

 smooth, or slightly warty scales ; (3) large irregular forms ; (4) 

 crosses ; and (5) bi-rotate forms. 



Si'EGiKic Diagnoses. 



Hidcsonella spiralis (Hickson) = Juncella spiralis Hickson. 



Colony unbranched ; in the larger forms spirally twisted. The 

 ccenenchyma is thin and densely packed with scale-like spicules ; 

 the axis is composed of concentric lamin* of a horny substance. 



