INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 53 



B. INVERTEBRATA. 

 MoUusca. 



Homologies of the Cephalopoda.* — Mr. J. F. Blake draws atten- 

 tion to some points in the anatomical structure of the various groups 

 of the MoUusca, and suggests that the arms of the Cephalopoda are 

 homologous with the opposite portion of the " architroch " to that 

 which forms the velum, and that they are another example of the 

 retention of primitive formations as functional organs. If this view 

 be correct it will be necessary to find elsewhere than in the arms the 

 part which is homologous with the foot of the other MoUusca, 

 Mr. Blake knows of only one structure which he can suggest, and 

 that is the median valve which is found within the funnel. 



An interesting fact to which the author calls attention is the 

 evidence which every new fact in the developmental history of the 

 Dibranchiate Cephalopoda affords as to the retention of their em- 

 bryonic stages by the Nmitilus. For example, not only is the funnel 

 of the Nautilus always, and that of the Dibranchiata during embryonic 

 stages only, formed of two distinct halves, but the ink-bag, which is 

 never found in the Nautilus, only appears late in the history of the 

 Dibranchiata, and the eye of the Nautilus remains permanently in a 

 condition which is transitory in the other group. Nor is this all : 

 the Tetrabranch has the auditory organs close to the eyes ; but in the 

 Dibranchiata the eyes gradually leave this position, and grow closer 

 and closer till they meet on the ventral side. The author inclines to 

 Valenciennes' view, that the eight or six processes on which the 

 tentacles of the Nautilus are found are homologous with the eight 

 arms of the Octopus. An interesting arrangement of the shell is 

 noted, and further details are promised in a forthcoming monograph. 



New American Cephalopoda.f — Among the numerous additions 

 recently made to the marine fauna of the eastern coast of North 

 America are two new Cephalopods, both belonging to the eight-armed 

 division. 



The more interesting one (^Stauroteuthis syrtensis) is the second 

 known representative of the remarkable family of Cirroteuthidfe, 

 characterized by the presence of a pair of fins, one on each side of 

 the body, supported by a transverse cartilage ; by the presence of a 

 great web surrounding and uniting all the arms nearly to their tips ; 

 and by the presence of two slender cirri between the suckers, along 

 the greater part of the length of the arms. This species differs so 

 widely from OirrotcutMs Miilleri Esch., the only representative of the 

 family hitherto described, that it is necessary to constitute for it a new 

 genus. 



StauroteutMs, gen. nov. 



Allied to Cirrotcuthis, but with the mantle united to the head 

 all around, and to the dorsal side of the slender siphon laterally 

 and ventrally. Fins triangular, in advance of the middle of the body. 



* 'Ann. and Mug. Nat. Hist.,' iv. (1S79) p. 303. 

 t 'Am. Journ. Sci. unci Arts/ xvlii. (1871t) p. 4(38. 



