MALACOZOA. CEPHALOPODA. FORAMINIFERA. 33 



Octopus Aldrovandi, Delle Cbiaje, Anim. di. Nap. iv. 57. I'l. 

 56. f. 2. — "Octopus Aldrovandi, Montfort, 8ur les Cephalop. 62," 

 — " Octopus leucoderma, Sangiovanni. Ann. des Sc. Nat. xvi. 315." 



ORDER II.— CEPHALOPODA SIPHONIFERA. 



Animal with a shell partially or entirely internal, and 

 divided into chambers by transverse partitions, through 

 which a siphon passes. To this order belong the families 

 of the Spiridhia, Nautilina, Ammonitina, and Belemni- 

 tina — of which no species have been found on the 

 Aberdeenshire coasts in a recent or Hving state. 



ORDER III.— CEPHALOPODA FORAMINIFERA. 



Animal bursiform, containing the shell in its hind 

 part ; the head very small, scarcely distinct from tbe 

 body, sometimes almost entirely enclosed in the anterior 

 folds of the skin, and terminated by numerous tentacula 

 forming several rows around the mouth, which is central. 



Shell many-chambered, altogether internal ; the last 

 dissepiment terminal ; no siphon, but only one or several 

 apertures between the different cells. 



Genus 1. Polystomella. 

 Shell discoid, subcarinate, many-celled ; the centres 

 umbilicate, the partitions numerous, forming grooves 

 radiating from the centre to tlie circumference ; the turns 

 contiguous, not apparent externally, being concealed by 

 the last ; the aperture of several holes or notches vari- 

 ously disposed. 



1. PolystomeUa crispa. Crenated Polystomella. 



Shell discoid, with both sides equally convex, carinated on 

 the margin ; the last turn entirely concealing the rest, of about 

 twenty cells, marked by flexuous ridges, the spaces between 

 which are crenated ; the aperture subcordate, closed. 



