l-SS MESSES. L. MURBACn AND C. SHEARER ON [Juiie 16, 



expect to find it in the other species when these are closely 

 studied. The four species of Gonionemus at pi'esent known are 

 as follows : — 



1 . Gonionemus vertens A. Agassiz (2). 



2. „ murbachii Mayer (29). 



3. ,, suavensis Agassiz & Mayer (3). 



4. ,, agassizii, sp. no v. 



In general appearance and structure the four species differ as 

 follows : — 



Gonionemus vertens has much the tallest bell and heaviest 

 tentacles, longest digestive cavity, and oval large marginal 

 papillae.— Pacific. 



Gonionemus murbachii has the bell low, the velum well 

 developed, the tentacles very flexible, the proboscis short, — 

 Atlantic. 



Gonionemus suavensis diflfers from the other species in the 

 presence of four green spots on the proximal ends of the radial 

 canals, in the absence of subumbrellar papillae, and the extent 

 and position of the ovaries. — Pacific. 



Gonionemus agassizii has the bell lower than in G. verie7is, yet 

 taller than in either of the other two species. It has a larger 

 number of tentacles (in fully grown specimens probably over a 

 hundred), which are shorter and smaller than in the other species. 

 The depression in the roof of the stomach is more marked in this 

 species than in the others with the exception of G. suavensis. — 

 Pacific. 



Species incerta. (Plate XX. fig. 2.) 



The following description refers to a peculiar form, a single 

 individual of which was collected by Prof. Kincaid at the 

 St. Paul's Island, Pribylofi" Islands. It is very badly pre- 

 served, and on this account no definite identification has been 

 attempted. 



Description. — The bell is 18 mm. high by 10 mm. broad at 

 its widest part, a little above the region of the velum. The 

 general shape and proportions of the bell are representee! 

 in PI. XX. fig. 2. The bell is drawn in somewhat towards 

 the mouth, and through this the smooth cylindrical proboscis 

 extends a short distance. The proboscis bears four well-marked 

 cylindrical mouth-lobes, one of these being much larger than 

 the others and rolled up on itself, looking like a small contracted 

 tentacle. 



Connecting the four radial canals and running in the bell- 

 substance are delicate transverse lines represented in the figure. 

 Some of these are larger than others, and look almost like small 

 connecting canals. The ludial canals are thick, and along then- 



