364 A. T. MASTEEMAN. 



Distal portion of subneural gland detached to form '' proboscis- 

 vesicle." Burrowing habitat. 



2. Diplochorda. — Mesomeres produced laterally into a 

 number of ciliated branchial tentacles, which in the adult point 

 upwards in front of the mouth, are supported by a chondroid 

 skeleton, and subserve ingestion of food. Metameres redupli- 

 cated by a dorsal flexure. Stomodseum with subneural gland 

 still opening to exterior, and extending into the subneural 

 sinus. Paired proboscis-pores near median dorsal line, arising 

 internally along the wall of the subneural sinus. Paired 

 notochords in pharynx, not displaced forwards. A short 

 oesophagus, stomach, and intestine. One pair of pharyngeal 

 clefts may (Cephalodiscus) or may not (Rhabdopleura, 

 Phoronis) be present, with chordoid walls. Ventral sucker 

 forming the organ of attachment throughout life. 



(1) Cephalodiscida. — Protomere persistent throughout life 

 as adhesive organ. Twelve pinnate plumes with eyes. Note- 

 chords and chordoid gill-slits persistent. Ventral sucker forms 

 budding organ. Habitat, creeping, sedentary, and coenoecial. 



(2) Phoronida. — Loss of protomere, atrial grooves, sub- 

 neural gland, and notochords in adult. Great development of 

 lophophoral tentacles (unbranched) and of chondroid tissue. 

 Paired nephridial apertures in metameres. Metamere elon- 

 gated, with circular and longitudinal muscles (as in Balano- 

 glossus). Permanent fixation by ventral sucker. Habitat 

 sedentary and tubicolous. Phoronis. 



(3) Rhabdopleurida. — Protomere persistent. No noto- 

 chord (?)^ nor pharyngeal clefts (?) in adult. Two pinnate 

 plumes. Attached by hypertrophied ventral sucker. Habitat 

 creeping, tubicolous. 



1 In the light of this interpretation of the organs of Cephalodiscus the 

 "notochord" of E-habdopleura requires renewed investigation, as it evi- 

 dently corresponds to the subneural gland of the former. Rhabdopleura 

 should, at one time in its life, have paired pleurochords, as in Cephalo- 

 discus. 



