152 



CTENOPHORA 



Key to the orders of Tentaculata: 



di Body more or less globose or cylindrical. 



&! Long tentacles present 1. CYDIPPIDA 



& 2 No tentacles in adult animal ; oral lobes present 2. LOBATA 



o 2 Body compressed and ribbon-like 3. CESTIDA 



ORDER 1. CYDIPPIDA. 



Body spherical or cylindrical or compressed in the plane transverse 

 to the tentacular axis; tentacles very long, on opposite sides of the 

 body, springing each from a deep pocket: several families. 



FAMILY PLEUKOBKACHIIDAE. 



Body spherical or ovoid, with the 8 ribs of equal 

 length: 4 genera. 



1. PLEUROBRACHIA Fleming. Body but very little 

 compressed; combs rather long but not reaching the oral 

 or aboral areas: about 8 species. 



P. pileus (Fabricius) (P. rJiododactyla Agassiz; P. 

 bachei A. Agassiz) (Fig. 249). Body about 20 mm. long 

 and 18 mm. wide, and very transparent; tentacles about 

 15 cm. long and white or rose-colored, with long pinnae : 

 from the south side of Long Island to Greenland ; breeds 

 in August and September; Europe; Pacific coast. 



P. brunnea Mayer. Body 12 mm. long, ovoid ; stom- 

 ach of an opaque yellowish-brown color; each tentacle 

 with a knob-shaped end: coast of New Jersey; rare. 



2. MERTENSIA Lesson. Body much compressed, the 

 tentacular axis being the wider; the 4 subtentacular 



combs longer than the 4 subventral ones: 1 American species. 



M. ovum (Fabricius). Body about 5 cm. long and ovoid in outline; 

 tentacles, combs, and sense organ light pink in color: Arctic Ocean to 

 New Jersey; rare south of Cape Cod. 



ORDER 2. LOBATA. 



Body ovate, compressed in the plane transverse to that of the stom- 

 ach; mouth wide, with a large and prominent oral lobe on each side of 

 it; at the base of each lobe is a pair of long projections called auricles; 

 tentacles of the ordinary kind wanting in the adultj but numerous, deli- 

 cate, filamentous tentacles may fringe the margin of the mouth and 

 the auricles; aboral sense organs sunk in a pit; a larval cydippiform 

 stage present, which has a pair of tentacles issuing from pockets and 

 in certain genera may have sexual reproduction: several families. 



Fig. 249 



Pleurolrachia 



pileus 

 (Mayer). 

 T, tentacles ; 

 C, combs ; 

 other refer- 

 ences as in 

 Fig. 248. 



