St. Andrews Marine Laboratory. 47 



off, leaving the young to develop during the winter. Young 

 and adult forms, however, occur throughout the summer and 

 autumn, so that the spawning-period is probably extended. 

 The great development of the lateral lobes of the oral region 

 causes a near approach to the Mnemia (Bolina) norvegica of 

 M. Sara. 



All the Ctenophores are thus found in greater or less abun- 

 dance throughout the year, and do not appear suddenly as young 

 specimens and disappear as suddenly as adults. 



3. On a Heteropod (Atlanta) in British Waters. 



Two years ago (May 1887) the capture of Clione in con- 

 siderable numbers in St. Andrews Bay formed a feature of 

 the season, and one which has not been repeated since, though 

 last year the water was persistently examined from January 

 to December. The frequent investigations of the Bay, how- 

 ever, in 1888 brought to light, amongst other things, a small 

 transparent univalve, like a finely fashioned shell of glass, 

 containing its inhabitant. It occurred in the midwater-net 

 opposite the Maiden B,ock on the 5th September, along with 

 a very rich and varied fauna, including Actinotrocha and 

 Appendicular ia. The specimen measured about T V of an inch, 

 and the aperture of the shell rather more than half this length. 

 It was not detected until immersion in spirit had taken place. 



In outline (Plate VIII. fig. 3) the form agrees generally 

 with that of Atlanta, such as figured by Souleyet in his fine 

 atlas *, in having a glassy, compressed, nautiloid shell, with 

 a narrow aperture and a prominent lip, which projects con- 

 siderably beyond the posterior coil. In a lateral view, indeed, 

 the aperture has a prominent and somewhat hooked prow (on 

 the left in the figure), from which a double curve proceeds to 

 the inner border. Two volutions and an incomplete third 

 seem to be present. 



When examined on edge (Plate VIII. fig. 4) the peculiarly 

 compressed condition of the shell is evident, the widest part 

 being at the posterior border of the lip, where it bends down 

 to join the spire. So far as can be judged from the outline 

 in this position, the posterior or whorled region of the shell is 

 flatter than the anterior. Moreover the free edge of the shell 

 is not keeled, as in so many of the foreign species, a flattened 

 margin being present all round. It must be borne in mind, 

 however, that this is probably a young example and that 

 considerable changes may ensue during growth. 



* Voyage autour du monde &c. sur la corvette ' La Boaite.' 



