28 THUIARIA SERTULAEIOIDES. 



Thidana phimidifera has a good deal of the habit of Hydrallmania falcata. 

 The pinna-bearing branches are regularly divided into equal internodes, 

 each internode carrying three hydrothecae and giving off a pinna from 

 alternate sides just above its proximal end. The pinnaB are much contracted 

 at their origin, and united to the branch which carries them by a very short, 

 nearly globular internode. The joints of the pinnae are at distant and 

 imcertain intervals. 



The hydrothecae at their distal ends are thin and collapsible, so that it 

 was very difficult to determine the true form of the orifice. In some cases, 

 however, where the parts were well preserved, it could be seen that the 

 thin collapsible portion was a tubular prolongation of the walls beyond 

 the true orifice, which was provided with two strong, broad lateral teeth. 



The gonangia had all fallen, but the indications of their attachment 

 were visible just below many of the hydrothecae. 



Thuiaria pinnata. 

 PL XV. Figs. 1, 2. 



Trophosome. — Stem attaining a height of nearly three inches, sparingly 

 branched, fascicled below, alternately pinnate ; pinnae given off at nearly 

 right angles to the stem, jointed at distant and uncertain intervals. 

 Hydrothecae borne both by stem and pinnae, deep cylindrical with 

 obscurely 4-toothed margin, adnate to the axis in their whole length. 



Gonosome not known. 



I)oiil)le-lioa(le(l Sliot Key from a depth of .S to 4 fathoms. 



Thuiana pinnata is a strong, rather rigid form, rendered somewhat 

 striking by the very open angle at which the pinnae are given off from 

 the stem. Some of the hydranths were well preserved in the speci- 

 men, and it would appear that they are capable of extending them- 

 selves far beyond the orifice of the hydro theca. 



Thuiaria sertularioides. 

 7V. XVI. Fiqs. 11, 12. 



Trophosome. — Ilydrocaulus attaining a height of three inches, slender 

 cylindrical, sending off short, simi)le branches which spring from the 

 anterior aspect of the axis. Ilydrotheca? opposite, with the distal half 

 free and divergent, gradually narrowing from the base to the orifice, 



