142 CCELENTERATA 



Key to the families of Hexactiniae here described: 



Oji Pedal disc absent ; usually sand dwellers 1. HALCAMPIDAE 



a 2 Pedal disc present. 

 &! Acontia absent. 



Ci Body tuberculated 2. BUNODIDAE 



c 2 Body not tuberculated 3. PAEACTIDAE 



6 a Acontia present 4. SAGABTIIDAE 



FAMILY 1. HALCAMPIDAE. 



Pedal disc absent, the lower end being rounded or pointed and often 

 swollen; mesenteries few in number, 6 pairs of protocnemes with 4 

 to 6 pairs of metacnemes being present; no special sphincter; tentacles 

 12 to 36: about 6 genera. 



1. HALCAMPA Gosse. Body long and slender with longitudinal 

 grooves and composed of 3 sections, an oral retractile portion, an inter- 



Fig. 228 Fig. 229 Fig. 230 



Fig. 228 Halcampa farinacea (from Parker). Fig. 229 Bicidium parasiticum 

 (from Parker). Fig. 230 Eloactis producta (from Parker). 



mediate portion usually coated with sand, and a pedal portion ; 2 siphono- 

 glyphs : several species, which live in sand and mud. 



H. farinacea Verrill (Fig. 228). Tentacles 12 in 2 rows; body 

 25 mm. long extended and 3 mm. in diameter; color whitish, with 

 longitudinal bands of brown; disc yellow: north of Cape Cod, in 8 to 

 10 fathoms. 



2. BICIDIUM Agassiz. Twelve tentacles in a single row; mouth with 

 a proboscis (conchula) : several species. 



B. parasiticum Ag. (Fig. 229). Body 30 mm. long extended and 

 6 mm. thick : parasitic on Cyanea, fixing itself by the mouth on the manu- 

 brium, subumbrella, or in the gastrovascular cavity; also in the sand: 

 Cape Cod to Bay of Fundy. 



3. ELOACTIS Andres. Body slender and very contractile; tentacles 

 short and blunt or capitate and in two rows : 5 species. 



E. producta And. (Fig. 230). Tentacles 20; body with 20 longitu- 

 dinal ridges, 25 cm. long extended; diameter 18 mm.; color whitish or 

 salmon : South Carolina to Cape Cod, buried in the sand or on the under 

 side of stones in shallow water. 



