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S^iicb^ta tavina (ep. novo). 



By John Hood, F.R.M.S. Plate XVII. 



IN March and April of this year (1893), I trawled out of the 

 waters of the Firth of Tay in great numbers a large rotifer 

 resembling in outward form the fresh-water species, Synchceta 

 t7-e??iula, Ehrn,, but which was much larger in size. It not only 

 differs in the nature of its habitat and in bodily dimensions, but 

 there is also a slight difference in the arrangement of the frontal 

 ciliary wreath ; the coronal cilia are arranged in cushion-like tufts, 

 very suggestive of the ciliary arrangement of Hydatina senta, with 

 the addition of a pair of small ciliated auricles, one on each side ; 

 these auricles are present to a greater or less degree in each 

 species of the genus Sync/i<xia. 



There are now eight or nine species of the genus known to 

 scientists. Seven of these have their corona formed in a more or 

 less convex or rounded shape. But S. tremiUa and the new 

 marine species — which I propose to call Synchceta tavina, after 

 Tavus, the classical name of the river Tay — have their corona 

 truncated, or flat across the frontal head, and each are furnished 

 with four long rigid bristles or styles, set nearly equi-distant on 

 the coronal head. Their function is probably that of feelers or 

 organs of touch. 



The chief characteristic and specific difference between other 

 species of Synchceta and the S. tavina is that the latter has two 

 occipital eyes, while all the other eight species possess one eye 

 only. The two eyes in S. tavina are set close together ; they are 

 of a dark reddish colour, situated on the lower lobe of the occi- 

 pital nervous ganglion or brain. 



The eyes are large and are quite readily observed from either 

 a dorsal, ventral, or lateral view. A nerve-thread leads from the 

 base of the brain to the dorsal antennae, situated in the neck. 

 There are a pair of y-shaped gastric glands at the top of the 

 stomach — one on each side of the oesophagus — which is peculiar 

 to S. tavina, whilst in all the other species the gastric glands are 

 round. 



The Mastax and the arrangement of the other internal organs 



