64 ART. 2, — H. MATSUMOTO : 



the basal vertebrae, G. tuberosus representing the first, G. arcticus 

 the second, and G. dolichodadylus the third. In G. tuberosus, the 

 floor of the gastral cavity is almost free from the basal vertebrae, 

 except in the very peripheral parts, where it is attached to the 

 one or two vertebrae just inside the disk border. In G. arcticus, 

 the floor of the gastral cavity is firmly attached to the basal ver- 

 tebrae within the disk, save one or two first vertebrae which are 

 free from the gastral wall. G. cariji and, according to Lyman, also 

 G, cJiilensis belong to this type. In G. doUchodactylus, the attach- 

 ments of the floor of the gastral cavity to the basal vertebrae ex- 

 tend from the second to the sixth vertebrae, so that the two com- 

 partments of the perihaemal canal plus genital bursa3 on either side 

 of a radius communicate together in two places, one lying inwards 

 just above the second vertebra and the other outwards just above 

 the sixth vertebra. In all the three types, the gastral cavity is 

 divided into ten radiating compartments, the radial and interradial 

 gastral pouches, of which the walls again present radiating folds 

 and are thickened by the presence of tlio inner layer of yellowish 

 or brownish glandular cells, the foldings and thickenings being 

 however more prominent in the second and third types than in 

 the first ; and the peritoneal cavity is perfectly divided into five 

 radial compartments, which are entirely fiUed up and obliterated 

 by the very voluminous, strongly folded generative glands. 

 The internal differences appear to me to be correlated with 

 certain external features ; the first type being characterised by 

 the high disk and strongly concave interbrachial ventral surfaces, 

 the second by the low disk and flat interbrachial ventral surfaces, 

 and the third by the very liigh outer ends of the genital slits. 

 Astrodendnim sagaminum is almost similar to the second type of 

 GorgonocephaJus in its internal structure. In Astrocladus anmdatus^ 



