root • or it may be likened to two round biscuits of unequal size connected by a short stout 

 pillar. Their true shape can only be seen when they lie on the side, an exceptional position 

 as they appear on the slide. 



Color. The colony is light grayish brown, the axis is dark brown, and the spicules colorless. 



The species can at once be distinguished from others in the collection by the spicules, 

 which are beautifully symmetrical and regular. A much larger specimen than the one described 

 as the type was secured at Station 258, and is somewhat darker in color. 



Thesea Duchassaing et Michelotti, (modified). 



Thesea Duchassaing et Michelotti. Memoire sur les Coralliaires des Antilles, i860, p. 18. 



Thesea Koliiker. Icones Histologicae, II, 1865, p. 137. 



Thesea Wright and Studer. Challenger Reports, the Alcyonaria, 1889, p. LVl. 



Echinogorgia (in part) Wright and Studer. Challenger Reports, the Alcyonaria, 1889, p. 120. 



The original definition for this genus is, in itself, inadequate for use under present 

 conditions of our knowledge. It is as follows : — 



"Le genre renferme les especes dont I'ecorce formee de squammules contient des spicules 

 tant a la surface qu'interieurement. Les cellules sont pustuliformes, disposees d'une maniere 

 subalterne sur les rameaux et ayant leurs parois formees par des squammes et une ouverture 

 terminale radiee". 



The writer goes on to explain that the genus is intermediate between Mnricca and 

 Priiiinoa, as originally defined. 



KÖLLIKER has studied the spicules of the type species, Thesea exserta (Ellis and Solander) 

 and has based his description of the genus on what he regards as the typical form of spicules. 

 His definition is as follows : — 



"Das Coenenchym zeigt oberflächlich grosse warzige schuppenartige Spindeln, die an der 

 Aussenseite mit grossen warzig-stacheligen Höckern besetzt sind, in der Tiefe kleinere warzige 

 Spindeln. Die Kelche sind wenig vortretend von Warzenform und zeigen ähnliche, nur etwas 

 kleinere Spicula als die Rinde. Deckel ähnlich wie bei Paraiimrkca nur klein, ganz flach und 

 wenig vortretend". 



The definition adopted in the present work is as follows : — 



Muriceids with low verruciform calyces, the walls of which are filled with broad scale-like 

 spindles, each of which is armed with thorn-like precesses on one side only, while the opposite 

 edge is merely tuberculate. These scales often have the appearance of imbrication, the toothed 

 sides of the spicules being uppermost and overlapping the lower edges of others. Heavy ordinary 

 spindles are also usually present. 



The type species of this genus is Thesea exserta (E. and S.). 



Other known species are Thesea (Echinogorgia) raiimlosa (Gray), Thesea (Muricea) 

 nmbraticoides (Studer) and the seven new species in the Siboga collection. 



It is altogether likely that other species included in the original genus Miiricea by the 

 earlier writers belong here; but the present writer is unable to identify them by the descriptions. 



