REPORT ON THE TUNICATA. 121 



In the two larger species (Culeolus wyville-thomsoni and Culeolus murrayi) the 

 branchiaJ aperture has a clearly-defined triangular form, with the apex of the triangle 

 directed posteriorly. In the other four species the shape is more that of a transverse 

 slit, but there is a tendency in all of them towards a triangular form. This is most 

 clearly seen in Culeolus recumbens, where the anterior or ventral lip is straight, while the 

 posterior or dorsal is strongly arched, forming an angle in the middle, and in Culeolus 

 moseleyi where the slit is cresccntic — the apex here, however, being anterior. 



In all the species the branchial aperture is situated on the dorsal side of the point of 

 attachment of the peduncle, and consequently in the four species in which the peduncle 

 turns dorsally the branchial aperture is to a certain extent hidden by it and looks more 

 or less downwards towards the bottom ; in Culeo/ns perlucidus, on the contrary.it is 

 directed upwards. 



The atrial aperture is a transverse bilabiate slit in all, and is situated towards the pos- 

 terior end. In three species, Culeolus murrayi, Culeolus wyville-thomsoni, stud Culeolus 

 moseleyi, it is quite posterior, while in the other three it is a little dorsal in position. 



In Culeolus iri/rille-tliomsoiii, the surface, though very uneven, is to the eye smooth ; 

 in the other species, however, it is rough from the presence of papillae or tufts projecting 

 from the surface of the test. In Culeolus perlucidus these are few in number and of small 

 size, but in the other four species they are larger, and in three of them, Culeolus murrayi, 

 < 'uleolus recumbens, and Culeolus perlatus, they are especially developed along a line 

 found the posterior end and surrounding the atrial aperture. Along this tract the 

 papillae are larger and more closely placed, so as to form a continuous band. Culeolus 

 moseleyi, finally, has the surface closely covered with papillae of moderate size, making it 

 equally rough all over. 



Culeolus recumbens is the only species which has sand-grains and other foreign 

 matter adhering to the surface of the body and peduncle, and it may be accounted for in 

 this case by the position the body must have had, lying on the bottom on account of 

 the weakness of the peduncle. 



The peduncle in all the species is thin but tough, smooth, and somewhat flexible 

 though stiffish, except in the case of Calculus recumbens, where, as above mentioned, it 

 i- weak and very flexible like a piece of string. In all, it is expanded slightly at the 

 lower end to form a base of attachment. 



The Test. — In all the species the test is of a cartilaginous consistency, though, in 

 -nine ,,{' fchem, especially Culeolus recumbens and Culeolus perlucidus, it becomes mem- 

 branous, on account of its thinness. 



The only notable peculiarities are in regard to the development and disposition of the 

 blood-vessels. In Culeolus murrayi they are feebly developed throughout the thickness 

 of the lest, but as compensation they expand at the outer surface into large closely placed 

 thin-walled chambers in communication with the large membranous hollow papillae. In 

 Culeolus wyville-thoinsoiii, on the other hand, vessels are numerous throughout the thick 



