THE LAMPREY. 7 



m.v), a slender rod, having the form of a T with a very 

 long stem, and situated in the middle line beneath the 

 lingual cartilage, the anterior ends of the two being con- 

 nected by fibrous tissue. 



1 6. The annular cartilage (Figs, i and 4, an), a stout 

 circular cartilage, supporting the oral funnel ( 21), and 

 giving attachment to the maxillary and mandibular teeth 



( M). 



17. The styliform cartilages (Fig. i, j/), two 

 elongated, tapering rods, attached by their thickened proxi- 

 mal ends to the posterior edge of the annular cartilage, a 

 little below its middle, and directed backwards and some- 

 what downwards. 



1 8. The branchial basket (Fig. i, d.c, v.c, ak, pc), 

 a cartilaginous framework supporting the gills. It consists 

 essentially, on each side, of (i) a longitudinal rod or dorsal 

 cartilage (d.c\ springing from the dorsal portion of the para- 

 chordal (b.fi), and passing backwards along the side of the 

 notochord ; (2) a second longitudinal rod or ventral 

 cartilage (v.c}, lying close alongside, and partly fused with, 

 its fellow of the opposite side, in the middle ventral line ; 

 (3) irregular transverse arches (a g, k) uniting the dorsal 

 and ventral cartilages and passing between the outer gill- 

 clefts ; (4) lateral longitudinal bars (/i, j) connecting the 

 transverse arches immediately above and immediately below 

 the gill-clefts; and (5) a cartilage (pc) supporting the 

 posterior and lateral walls of the pericardium. 



Each of the transverse arches, except the first and the eighth or 

 last, consists of seven well-marked portions; of these, the first or 

 dorsalmost (a) and the seventh or ventralmost (g) are flattened plates, 

 produced into longer or shorter anterior and posterior processes; the 

 second (b) and sixth (f) are short curved rods ; the third (c) and fifth 

 (<?) are flattened, and are produced into forwardly directed processes ; 

 the fourth or middle portion (d) is a curved rod situated immediately 



