108 



CCELENTERATA 



common; New Jersey to the Arctic Ocean from low-water mark to 100 

 fathoms, usually in rather deep water; Pacific coast; Europe. 



T. cupressina (L.). A slender, elongated 

 colony, often 20 cm. high, branching alter- 

 nately and dichotomously ; gonangia elongate 

 with a prominent spine at each side of the 

 aperture: same habitat as the preceding but 

 less abundant. 



6. HYDRALLMANIA Hincks. Hydrothecae 

 in a single row - projecting out from the 

 hydrocaulus alternately to the right and the 

 left; colony pinnately branching: 3 species. 

 H. falcata (L.) (Fig. 179). Colony often 

 30 cm. high, slender, rather rigid and with 

 simple branching; on each branch the second- 

 ary branches are very regular and feather-like; 

 gonangia ovate and simple: on stones, shells, 

 fJ5&a (2^T"AT5S etc., on New England coast and in Long Island 

 Sth!.' branCh Wlth hy ~ Sound; Puget Sound; Europe. 



FAMILY 2. PLUMULARIIDAE.* 



Trophosome: usually a branched colony with sessile hydranths, 

 which are borne in a row on small branches called hydrocladia (Fig. 180) ; 

 between the hydranths and on the main stem and branches are nemato- 

 phores, small specialized defensive polyps, each of which consists of a 

 hydrotheca and an elongated body armed with nematocysts. Gonosome : 

 gonangia large, the blastostyles producing planulae and never medusae : 

 about 43 genera and over 300 species, being a quarter of all known 

 hydroids; about 100 species occur along the Atlantic coast and in the 

 West Indies. 



Key to the genera of Plumulariidae here described: 



01 Gonangia not protected by special branchlets ; nematophores trumpet-shaped 



and movable. 



&i Hydrocladia do not branch. 

 G! Colony not dichotomously branched ; the hydrocladia arranged in whorls 



or scattered along the stem 1. ANTENNULABIA 



c. Branching dichotomous ; hydrocladia all arise from the upper side of 



branches 2. MONOST^ECHAS 



Z> 2 Hydrocladia forked 3. SCHIZOTRICHA 



2 Gonangia protected by special branchlets ; nematophores immovable. 



4. CLADOCARPUS 



* See "American Hydroids, Part I, The Plumularidae," by C. C. Nutting, U. S. 

 Nat. Mus. Spec. Bull. No. 4, 1900. 



