Identi'f cation of the Species o/'Cephalodiscus;. 409 



Tlie only specie-s outside the siil)j>;enus Deiniolhecia tliat 

 lias spines on the ccenoecium is C. (jUchristi. 



The length of the zooids given in the key is that from the 

 free ends of the aims to the end of the truidc, not including 

 the stalk. 



I. Cavities of the coencecium iu the form of tubes. 

 Each tubular space witli a sin^^le oritice, and 

 occupied by oue zooid and its buds. Arui3 

 without end-swelUngs and refractive beads, 



A. Canirecium in tlie form of a branching; 

 system, witli the newest tubes at the apices 

 of the branches Idiothecia. 



a. Internal ends of the tubes communicating 



by a labyrinthic system. 



1. Brandies massive, fragile, with abun- 

 dant fragments of shell embedded ; 

 each ostium with a short, blunt lip, 

 but no peristomial tube. Zooids 

 4-'5 mm., blackish ; arms 8 or 9 pairs . ayyliUinans. 



b. Internal ends of tlie tubes blind. 



'2, Branches massive, fragile, with abun- 

 dant fragments of shidl embedded; 

 each ostium with a short peristomial 

 tube. Zooids 3'o mm., white ; arms 

 usually 8 pairs ev<imi. 



3. l^ranches fairly long, slender, not tragi le, 



with numerous long spines, brownish ; 

 ostia with or without peristomial tubes. 

 Zooids r6 to IS mm., blackish when 

 alive, brown in preserved material, 

 with blackish margin to anterior edge 

 of shield ; arms usually 6 pairs .... gilthristi. 



4. Jiriuiches medium or slender, orange- 



coloured, nospines ; each ostium witha 

 .»«ingle-li Piled peristomial lube. Zooids 

 2--') mm., whitish ; arms pairs .... levinneni. 



5. Branches massive, rarely slender, greyish 



or brownish, no spines ; each ostium 

 with a short, single-lipped peristomial 

 tube. Zooids 40 to 6 mui., blaikisii ; 

 arms usually 7 pairs, each with two 

 black bands along the a.xis nifft-escrns. 



J». L'ccncecium in the form of a hemisphere, 

 cone, or cake, with the newest tubes at the 

 edges ; basal ends of the tubes blind .... OrtluHcuji. 



G. Colony bulky and massive, tubes long, 

 common cceiueciHl substiince lirm ; 

 each ostium with a single thick lip, 



Ann, ct- May. N. I list. tSer. D. Vol. v. 28 



