of the Bay of Naples. 105 



this species no trace of the rotatory organ has been retained — 

 a phenomenon which is one of the greatest rarities in the 

 class Rotatoria. Further, the head is somewhat different in 

 form from that of P. asplanchnus^ inasmuch as it is much 

 attenuated in front, so that the buccal aperture is situated at 

 the apex of a small cone. This species is much scarcer than 

 P. asplanchnuSy and I have seen only two female examples of 

 it. The measurements of one of these were as follows : — 

 Head 0*12, neck (almost extended) 0'12, trunk 0*18, tail 0*2. 



3. Paraseison proboscideus, sp. n. 



Also, like the preceding species, possesses no buccal feelers, 

 but, on the other hand, the head is characterized by the presence 

 of a small naked proboscis, which is situated above the buccal 

 aperture and appears to act as a tactile organ. I think I have 

 observed tliat this proboscis was connected by a delicate cord 

 (canal ?) with the yellowish-green body which I have already 

 mentioned in Paraseison asjilanchnus. The masticatory appa- 

 ratus differs somewhat in form from that of the common 

 species. In the musculature surrounding it we observe some 

 bands, arranged transversely and parallel to each other, which 

 never caught my attention in P. asplanchnus. When fully 

 extended, the single female that I have observed measured 

 about 0"76 millim. 



4. Paraseison ciliatus, sp. n. 



This species I have only twice seen living, but have often 

 been able to examine in preserved material. In some points 

 it greatly resembles Seison Oriibii, Glaus, so that at first I was 

 in doubt whether it might not be identical with that form. 

 Like the species in question it has, on each side, to the right 

 and left of the buccal aperture, a strong tuft of cilia, by the 

 rapid movement of which the animal's food is swept in. 

 There are, however, no tactile seta3 in the vicinity of the 

 mouth. A further agreement with the true Seisonidse is to be 

 found in the fact that the matrix of the cuticle shows two 

 streaks of changed constitution on the two sides of the ventral 

 surface of the trunk. Each of these longitudinal bands is 

 about 0*017 millim. in widths and bears a great number of 

 transverse, parallel, and very delicate fibrils, between which 

 comparatively numerous nuclei are placed. These trans- 

 versely striated parts extend in the species of Seison over the 

 whole ventral surface of ihe trunk, while in our animal they 

 enclose between them the greater part of it unaltered in 



