14 Mr. H. J. Carter on new Species of Hydirsictmnd^. 



erect habit, and in the form and position of its hydrothecge, that 

 it must be considered the type of a new genus, to which I 

 have given the name of Chitina and designated the species 

 ericopsis, from its being so much like the stems of the common 

 heather here used for making brooms. 



These species may be provisionally tabulated thus : — 



Family Hydractiniidae. 

 Incrusting species : — 

 Hydractinia ecMnata. 

 H. levispina. 



Branched procumbent species: — 

 Ceratella fusca^ Gray. 

 Dehitella atro7'uhens^ Gray. 

 Ceratella procumbenSjXi. sp. 

 C. spinosaj n. sp. 



Branched erect species : — 



Chitina ericopsis^ n. g. et sp. 



In this way I hope to get rid of them from among the Spon- 

 giadse, and to bring them to the notice of those who have 

 specially devoted their attention to the Hydroid Zoophytes. 



EXPLANATION OF PLATE I. 



Fig. 1. Upper and lower surfaces respectively of a turbinated (?) shell 

 whollij transformed into clathrate chitinous fibre structure by 

 Hydractinia levispina (n. sp.): a, upperside; b, lower side; c, 

 smootli area on the latter, produced by fi-iction during the time 

 the shell was tenanted by a Par/iuus ; d, tubercular excrescences 

 of the chitinous structure involving one or more spines, which 

 the dark points (e) are intended to represent ; //, line of section. 

 Natural size. 



Fig. 2. Section of the same through the line//, fig. 1, showing that the 

 columella and every particle of the original shell-substance has 

 been replaced by the chitinous structure : a, right side ; b, left 

 side ; cc, layer surmounted by spines (J f?) projecting owilwarcfe; 

 e e, surface-layer of the cavity. Natural size. 



Fig. 3. Hydractinia levispina, n. sp., spine of, with portion of subjacent 

 clathrate structure at its base, showing that it is merely a conical 

 form of the latter ; magnified. Real length of spine about 

 l-30th inch, diameter of base of spine l-60th inch. To contrast 

 with the serrated form of the following figure. 



Fig. 4. Hydractinia echinata, spine of, about the same size as the fore- 

 going. To contrast with fig. 3. 



Fig. 5, The same, incrusting Buccinmn undatum, which contains the re- 

 mains of a Pagurus. Magnified portion of lower surface of a 

 fragment of the crust, raised by contraction and fracture from the 

 inner surface of the outer lip close to the canal, showing that it 

 is composed of calcareous matter, through which points of the 

 superincumbent chitinous structure (a a) project. Horizontal 

 view. 



