218 M. C. Mereschkowskj on some 



cina. and the latter having it strongly emarginate on one side 

 (besides the suckers in two bundles). Nor can Acineta Sai- 

 fiilce be confounded with A. patula, on account of the diffe- 

 rence in the form of the carapace, and the extreme fineness of 

 the part of the peduncle where it unites with the carapace. 

 The same difference of form distinguishes my species from 

 Acineta vorticelloides^ Fraip., with a very open and, '' so to 

 speak, rudimentary "'^j carapace. Lastly, a crenulation upon 

 the lateral surfaces and the irregularly-cut free margins 

 of the carapace of Acineta crenata^ Fraip., prevent its 

 being confounded with our species. There only remains^ 

 therefore, Acineta divisa^ Fraip., with which my species has 

 the greatest analogy, as may be seen from the description 

 given of it by Fraipont. The following, however, are the 

 differences that may be found between the two species. In 

 the first place, the general form of the body in A. Sa'ifulce is 

 usually mucli elongated, which is the case only exceptionally 

 in A. divisa, the carapace of which is generally very wide open, 

 approaching rather in form that of A. patula. Then the surface 

 of Aciiieta Sa'ifuloi is always ornamented with transverse 

 strise, which is never the case in A. divisa. Lastly, the inte- 

 rior cup, the bottom of the second carapace, is much deeper 

 iu my species than in Fraipont's, which is in relation to the 

 more elongated general form of the carapace in Acineta 

 Sa'ifulce. 



To sum up, it may possibly be that we have to do here 

 only with varieties of a single species, which would thus have 

 to bear the name of Acineta Saifalee, as having been given 

 earlier tlian the other name. But until we have more detailed 

 observations I feel compelled to retain the two separate species. 



Anisonema quadricostatum^ sp. n. 

 (PI. XII. fig. 12.) 



Diagn. Body oval, strongly depressed, and furnished on 

 the dorsal surface with four ribs. 



Loc. Bay of Naples, Sorrento. 



Descr. The oval body is characterized by its strong depres- 

 sion ; the cuticle, which covers the whole body, is very firm, 

 and in the dorsal part it forms at the surface four longitudinal 

 elevations, four ribs, slightly spirally curved. The mouth, 

 which is widely open in the form of a vertical fissure, is 

 very visible on the ventral surface, from which originate two 

 flagella, one of which, trained along behind, attains two and 

 a half times the length of the body. 



* Eraipont, /. c. p. 92. 



