Introduction to Animal Morphology. 153 



surrounded by a ring of ten plates, and both at the narrow 

 end of a flask-like body ; ambulacral canals in five double 

 rows, each with two sets of little feet and two Polian vesicles ; 

 tentacles 10; the single sex-opening is at the top of the 

 neck. This includes one species Rhopalodina lageniformis 

 from Congo. 



3. Dipneumona, Pneumonophora {Brandt) have two tree- 

 like water-lungs and Cuvierian organs ; the mouth and anus 

 are polar, and the ambulacral rows are never double. This 

 includes three families: — i. Liodermatidae — footless, with 

 twelve shield-like tentacles (Liosoma), or ten single cylin- 

 drical (Haplodactylus) or branched tentacles (INIolpadia). In 

 this genus, the csecal sacs of the water-vascular system end 

 in the skin, but are not prolonged into pedicelli. 2. Dendro- 

 chirotas — tentacles branched, unequal ; they may be sporadi- 

 podous, homoepodal, with ten(Thyone), twelve (Phyllophorus), 

 or fifteen retractile tentacles (Orcula) ; rarely stiff" (Sclero- 

 dactyla) or heteropodal, with twenty tentacles (Cladolabes) ; 

 or the feet may be stichopodous in five rows, with twenty 

 (Thyonidium) or ten tentacles. The feet in each row are 

 uniserial, retractile (Ochnus), or non-retractile (Perlinus) ; or 

 they may be in 2-6 series with equal (Cladodactylus) or 

 unequal (Dactylota) ; or they may be tristichous (Psolus, 

 Cuvieria). 3. Aspidochirotae — tentacles shield-like ; Cuvierian 

 organ caecal, well developed ; feet pentastichous (Aspidochir) 

 or heteropodal ; those of the trivium suctorial at the end ; 

 those of the bivium conical (Stichopus), or sporadipodal, 

 homoeopodal (Sporadipus), or heteropodal ; abdomen swollen, 

 as in Trepang (the edible Chinese form), or flat, with a round 

 (Holothuria), five-angled, toothless (Bohadschia), or five- 

 toothed anus (Actinopyga). 



