22 SIPHONACE^. 



Ashmead. Conch Key and Key Biscayne, Frof. Ttionmj. — Var. ^ cast ashore at 

 Key West. W. H. H. (v. v.) 



SurcuU prostrate, robust, sometimes nearly as thick as a goose's-quill, sometimes as 

 a crow-quill, glabrous, glossy, shrinking much in drying and becoming longitudinally 

 furrowed, vaguely branched, rooting at intervals of one or two inches ; the root long, 

 branched, and fibrilliferous. Fronds rising from the upper surface of the surculi 

 scattered, on long, glabrous, naked stipites, flabelliform in outline, pedate or digitate, 

 the branches spreading, simple or forked, fastigiate, densely set throughout with 

 imbricated, four or five-ranked ramenta. Rammta one to four lines long, varying 

 much in length and somewhat in ramulification on different specimens. Normally they 

 are patent or recurved and sub-bipinnate, or pinnate with pectiniform pinnules ; that 

 is, the ramentum is oppositely pinnate, the pinnas closely set, straight, subidate, or 

 filiform, mucronulate, and furnished along one (the lower) side with unilateral ramuli 

 of similar form. In different specimens the number and development of the processes 

 of the pinnae vary ; sometimes they are 5 or 6, and of considerable length ; some- 

 times but 2 or 3, and these very short. In var. y8 they are absent altogether, and 

 the ramenta of much greater length than is usual in var. a ; but I have seen speci- 

 mens so completely intermediate that I dare not make two species of these seemingly 

 different forms, particularly as both occur in the same locality. The normal form 

 has been admirably figured by Bory in the plate above quoted. I fear that C. phhe- 

 oides of that author can only be regarded as a variety of the present species. 



II. IIALIMEDA. Lamour. 



Root fibrous, much branched. Frond erect, dendroid, branching, articidato-con- 

 stricted, with flattened internodes (or articulations), coated with a smooth calcareous 

 crust, and composed internally of a plexus of longitudinal, sub-parallel, unicellular, 

 branching filaments. (These filaments, which constitute the medullary stratum of the 

 compound frond, are constricted at intervals, and at each constriction emit a pair of 

 opposite, horizontal, di-trichotomous, corymbose ramelli, whose apices cohere together 

 into a false epidermis or periphery.) 



The species comprised in this genus were placed by Ellis and Linnaius in the genus 

 Corallina, where they remained till 1812, when Lamouroux very properly separated 

 them to form the present group. The resemblance to Corallina is merely external. 

 Both genera have jointed fronds, encrusted with calcareous matter, but here tlic resem- 

 blance ceases. The structure, colour, substance and fructification, which determine 

 affinities, are widely different in Corallina from what they arc in Halimeda. In this 



