22 



and were of massive build, but with no approach to the 

 caudate character assigned to this species; the colour was 

 yellow, with patches of rusty-pink ; the spiculation was per- 

 fectly specific, as were also the calcareous ring and the 

 tentacles. 



At the other end of the scale w^e got individuals of about 

 70 mm. in length, white in colour, and markedly caudate, 

 the "tail" portion being one-half the length of the animal, 

 and constricted abruptly at its junction with the body; the 

 ring, ossicles, and tentacles were specific. The remaining 

 specimens furnished links between the two extremes given 

 above. 



We do not at present propose to enter upon a taxonomic 

 review of the family Molpadiidae, but would point out that 

 this great variation in form occurring in one species makes it 

 doubtful whether the division into the tw^o genera Moljjadia 

 and Gaudina is justifiable. 



On some Structures found in the Pharynx of 

 Thyone vercoi, n. sp. 



In making the necessary dissections for the identification 

 of the several species contained in this collection, our atten- 

 tion was drawn to some very unusual structures occurring in 

 the pharynx of Thi/one vercoi, n. sp. The pharynx, on being 

 opened, displayed a large number (over 100) of small 

 pedunculated processes depending in several somew^hat 

 irregularly disposed rows from the whole of its inner surface 

 (plate ii., figs. 2, 3, and 4; plate iii., fig. l,e,f,g; plate iv.). 

 These processes measured from 2 to 4 mm, in length, and aver- 

 aged about 1 mm. at their greatest diameter. Their colour was 

 a dead white, and they were very conspicuous. The white 

 colour was shown by microscopical examination to be due to 

 a dense aggregation of calcareous particles, foliaceous in form, 

 and measuring about 0'048 mm. in length (plate iii., fig. 

 l,e,f,gj. These particles coalesced to form a reticulated mass in 

 the interior of the process. After decalcification, longitudinal 

 sections were cut of one of the processes with a portion of 

 the pharyngeal wall from which it depended. The wall of 

 the pharynx was found to be histologically normal; the pro- 

 cesses were extensions of this normal tissue, the longitudinal 

 muscles not being, however, continued into them, but pro- 

 •ceeding in a direct line along the pharyngeal wall. The con- 

 nective tissue of the interior of these processes was almost 

 entirely replaced by the mass of ossicles already referred to. 

 The structure cannot be homologized with any part of the 

 recorded anatomy of Holothurians, but a remark by 



