THE ENTEROPNEUSTA. 639 
The right and left peripharyngeal spaces are separate except at the hind end of the 
collar, where they meet ventrally. As they reach forwards their ventral borders slope obliquely 
and gradually upwards until the two borders merge at a spot dorsal to the cesophagus, 
where the circular muscles which the spaces contain are inserted into the nuchal skeleton. 
Where the peripharyngeal spaces are deficient ventrally the wsophagus is still provided with 
a layer of circular muscles probably derived from the longitudinal musculature. 
Branchial region. One of the chief characteristics of the present species as compared 
with the other members of its family lies in the fact that the branchial portion of the 
esophagus is of considerably less extent than the remainder (Pl. XLII. fig. 13). This results 
in the septal and tongue bars being relatively short. The musculature is in this region 
well-developed. Beneath the powerful longitudinal layer is a sheath of circular fibres extend- 
ing up to the lower ends of the gill pouches. Noteworthy is the position of the ventral 
nerve cord which projects so far inwards that it almost abuts against the circular muscles. 
Of the posterior branchial region it is not possible to give any account, since I have been 
unable to identify it among the fragments which have come to me. Synapticula are absent. 
The first three gill pouches are dorsally confluent, forming a chamber with a single external 
pore into which opens the collar pore. No trace of truncal pores is to be found resembling 
those described by Willey (99, pp. 273, 280) for Spengelia. The branchial region is 
probably devoid of gonads, or if these occur here it is only in its most posterior portion 
that they are to be found. In the specimen with the greater attached length of branchial 
region, this was about 44 times the length of the collar. 
at the extreme end of this fragment. 
No gonads were present even 

Schizocardium 
Glandiceps 
Spengelia 
Willeyia 

Pericardial auricles very 
large. 
No dermal genital pits. 
chial sac very small. 
Peripharyngeal cavities. 
Cornua of nuchal skeleton 
to posterior collar re- 
gion. 
No median gonads. 
Synapticula. 
External liver saccules. 
Ventral proboscis septum 
long and reaching ver- 
miiform process. 

(Esophageal part of bran- | 
Pericardial auricles very 
small. 
No dermal genital pits. 
(Esophageal part of bran- 
chial sac reduced to a 
broad tract. 
Cornua of nuchal skeleton 
to posterior collar re- 
gion. 
Median gonads present or 
absent. 
No synapticula. 
No external liver saccules. 
Ventral proboscis septum 
short and not to vermi- 
form process. 

No peripharyngeal cavities. 
Pericardial auricles small. 
| Dermal genital pits. 
(Esophageal part of bran- 
chial sac a deep groove. 
Peripharyngeal cavities. 
Cornua of nuchal skeleton 
to posterior collar re- 
gion. 
Median gonads present or 
absent. 
Synapticula. 
External liver saccules 
present or absent. 
Ventral proboscis septum 
short and not to vermi- 
form process. 

Pericardial auricles small. 
No dermal genital pits. 
(Esophageal part of bran- 
chial sac much larger 
than branchial part. 
| Peripharyngeal cavities. 
Cornua of nuchal skeleton 
not found in posterior 
half of collar. 
No median gonads. 
No synapticula. 
(?) 
Ventral proboscis septum 
very long but not to 
vermiform process. 



Genital region. The longitudinal muscles are still strongly developed (Pl. XLII. fig. 14) 
but the circular layer has now disappeared. The ventral nerve cord still shews the peculiar 
82—2 
