658 
R. C. PUNNETT. 
is always complete after the first root. 
The ventral septum is a more conspicuous structure 
in this species than in most others of the genus. It is always found in the posterior part 
of the collar and may reach forwards over 4 of the collar length. 
TABLE 6. 
Pt. asymmetrica. 








No. of specimen (1) (2) (3) (4) (5) 
Proboscis coelom............+-s-+e+-« Very small as (1) Well marked as (1) Obliterated by 
but small muscles 
Collanicoelom\cennceas-sesrssesseoeee Much reduced Almost Fairly spacious} Very small Well marked 
obliterated 
Ventral proboscis septum ......... Short. Not | Not to tip of | Not quite to as (3) as (1) 
nearly to tip of | stomochord tip of 
stomochord stomochord 
Dorso-ventral proboscis muscles Absent as (1) as (1) as (1) as (1) 
Dorsal collar septum ............... Complete after as (1) as (1) as (1) as (1) 
Ist root 
Ventral collar septum ............ Complete in as (1) as (1) as (1) Complete in 
hind end of posterior 4 of 
collar collar 
RaCemose Oran) ..-..<.--tasssceeeres Large but Large and as (1) Small and | Very large and 
unlobulated lobulated unlobulated lobulated 
Dorsal proboscis muscle decuss- | Well marked. as (1) as (1) Not well as (1) 
ation No ventral cir- marked. No 
cular muscles ventral circular 
muscles 
Dorsal \OObS ss sneseresse secre ome eceeee *RRR RRrr RR R RR 
IBrOHOSCIS POLES eecpess-cseessree eee *LR Lr 1R IR IR 
IN Gives Cord: hr scerss- ses cocs-ose meets Lumen almost |Lumen distinct| Lumen distinct as (1) as (1) 
obliterated in places in places. 
Strong tendency 
" to obliteration 
ength of post-branchial groove Bs , . 
Length of branchial region ou ay ee um 
Length of cornua x 100 : ! : 
Reaeiioncallaae ae 245 20°9 47°3 40°5 25°7 
Circumference of branchial ces. 98 1-08 1-04 -s 1-06 
Circumference of cesoph. ces. 
SYMAP HCW cesecssstsecsosesceseses -- -- Not more than 5 _— = 









The lumen of the collar cord is never continuous throughout. It may be present as 
a number of small cavities much broken up, or it may be practically absent, the cord shewing 
* See foot-note on p. 645. 
