982 MR. W. M. THOMSON ON A BRANCHIATE [Dec. 18, 



Within the lips are seen the four dark brown teeth or jaws *, 

 a dorsal pair and a ventral (Plate LXII. fig. 13); but in this front 

 view only the terminal claw-like tip of the tooth can be seen, 

 its base, hidden in a muscular cushion (e), can only be seen by 

 slitting up tbe wall of tlie pharynx. 



Each tooth springs from a wide, somewhat triangular base of 

 greenish-brown colour, less hard than the actual tootb, and marked 

 by a series of concentric lines like a lamellibranch shell. The 

 right and left tooth of each pair are connected by what is, no 

 doubt, a secondary formation of calcareous material deposited on 

 the convex side of each claw (c) ; this additional matter increases 

 in thickness backwards, till the two touch and fuse. 



The outer margin of the base of the tooth dips down into an 

 elongated slit-like pit between itself and the muscular cushion (>). 

 This cushion is continued anteriorly into a small, reflexed, papilla- 

 like structure fitting against the concave side of the claw-like tip of 

 the tooth ; the latter projects — when at rest — into a pit anteriorly, 

 immediately behind the lip, which is now seen to be in reality the 

 hinder end of the thin-walled, eversible buccal region (//). 



The ventral teeth are almost identical with the dorsal pair. 



It may be as well to mention that the base of the tooth («) is 

 hollow, and occupied by a mass of muscle after the fashion usual 

 in annelidan jaws or teeth ; further, the internal root of the 

 claw-like tooth is produced into a longer and narrow plate for the 

 attachment of muscles, but which is not represented in the drawing, 

 as it is embedded deep in the wall of the pharynx. 



Localities. — Specimens were received from Otago Harbour on 

 the east coast of the South Island of New Zealand, captured under 

 stones and also taken from the stomachs of fish. Others were 

 obtained from various stations along the east coast of the South 

 Island, as far north as Tasman Bay, where they were brought up 

 in the trawl from depths of 10-30 fathoms. The specimens 

 named by Kirk [8] were collected in "Wellington Harbour, North 

 Island. It is evidently of wide distribution along our coasts. 



Those from different localities varied considerably in colour : 

 some were uniformly dark coffee-brown, above and below; while 

 others were yellowish white below, and a warm brown dappled 

 with light buff on the dorsal surface. 



The elytra are in some specimens thickly covered with muddy 

 particles attached to the spines, the notopodial hairs being 



1 I would suggest the word " stomatognath " as a convenient term by which 

 to refer to the various cbitinous, or calcified, or siliceous " teeth " or "jaws" 

 occurring as specialized thickenings of the lining of the stomodieum, such as 

 the teeth or jaws of Annelids, including Leeches ; the " teeth " in the gastric 

 mill of Crustacea; the elements of the " mastax " of Kotifers ; the individual 

 members of the radular apparatus of Mollusca ; and possibly, also, the horny 

 teeth of Cyclostome fishes. The word was used by me some years ago, in a 

 course of advanced lectures on the Annelida that I gave in the University of 

 Oxford ; and it appears to me that some such word would be useful in referring 

 to these and kindred structures. — W. B. B. 



