REPORT OX THE TIJXICATA. 
135 
Cystodytes, von Drasche. 
Distoma, Della Valle, Contribnzioni, &c. p. 40, Xapoli, 1877. In part. 
Distomvs, Della Valle, Xuove Contribuzioiii, &c., Roma, 1881. In part. 
Cijstodytes, von Drasche, Die Synascidien der Bucht von Rovigno, p. 18, Wien, 1883 (as a 
snbgenns of Distoma). 
Colony of irregular form, attached and in crusting, sometimes lobed, and of 
moderate thickness. 
Ascidiozooids surrounded bv capsules formed of calcareous disk-shaped spicules. 
No vascular appendages present. 
Test cartilaginous, containing calcareous disk-shaped sj^icules. 
Braruchial Sac small. 
Abdomen as large as thorax. 
Dr. E. von Drasche, in his Synascidien der Bucht von Eovigno, distinguished two 
new species of Distomidae as having a remarkable form of calcareous spicule wdiich clearly 
separated them from all allied forms. On this account he divided the old genus Distoma, 
to which these new forms belong in their other characteristics, into two suljgenera, 
Cystodytes and Distoma. Previously, however, Della Yalle had described and figured ^ 
a form of spicule occurring in Distoma dellechiaicB, from the Bay of Naples, which is 
apparently the same as those of Cystodytes. In the Challenger collection there are two 
additional new species which agree in all essential characteristics of generic value with 
V. Drasche’s two species of Cystodytes and with Distoma dellechiaice, Della Valie, and I 
consider that as these five species are so clearly distinguished from other Distomidae it 
will be of advantage and will simplify classification if Cystodytes as defined by von 
Drasche be considered an independent genus. 
The colony is in all cases of somewhat irregular form and moderately large size. 
It is attached by the greater part or the whole of its lower surface, and the upper 
surface may be either nearly flat or raised so as to form a convex mass of moderate 
thickness. The species from the Adriatic are of rather greater thickness than those in 
the Challenger collection : Cystodytes cretaceus may be as much as 3 cm. in thickness. 
The colour varies considerably. It may be milk-wdiite, grey, yellow, brown, or violet. 
The surface is always smooth. In von Drasche’s two species the Ascidiozooids are 
arranged in distinct systems. This is not so obvious in the Challenger species. 
Cystodytes draschii shows in some places the formation of irregular systems, but in 
Cystodytes pliilippinensis there seems to be no definite arrangement. The most 
characteristic feature of the genus is the formation, around the greater part of the body 
of each Ascidiozooid, of a calcareous capsule formed of separate discoidal plates which 
^ Nuove Contribuzioiii, &c., p. 23, Tav. ix. figs. 98, 99. 
