CEPHALOPODA. 19 
of eight arms, and two additional elongated tentacula. In this tribe the suckers are 
armed, and the mantle supports two lateral or terminal fins. The ‘‘ Octopoda’ were 
divided into two families, termed “ Wuda” and “ Testacea,” according to the absence or 
presence of an external shell. In the second family was placed Bellerophon, an extinct 
genus proposed by De Montfort for remains peculiar to the Paleozoic series, which 
Defrance had associated with Argonaut, but which subsequently had been considered 
as belonging to a heteropodous mollusc. The reasons which induced Professor 
Owen to restore Bellerophon to a‘place among the Cephalopods are not stated. If 
however, its remains belong to this class, they present the anomaly of the testaceous 
Octopods having been without a representative from the end of the carboniferous 
epoch until the deposit of the newer tertiary formations, when the family reappears in 
the genus Argonaut. The decapodous Cephalopods were divided into four families, 
according to the position of the fins, the nature of the internal shell, and the condition 
of the infundibular cartilage. The ordinal and sub-ordinal distinctions of Professor 
Owen have been adopted by M. Deshayes, but that naturalist has subdivided the 
Octopoda and Decapoda each into two groups; the Octopoda according to their 
possessing one or two rows of suckers, and the Decapoda according to the position of 
the fins. These characters appear to be of secondary importance, and, by themselves, 
can scarcely be considered as sufficient for more than generic distinctions. M. 
d’Orbigny has availed himself of the presence of suckers and tentacles, characters 
originally proposed by himself and M. Ferussac as ordinal distinctions, and accordingly 
the Cephalopoda are divided by him into Acetabulifera and Tentaculifera. The sub- 
ordinal distinctions of Professor Owen are adopted by this author ; but in his subdivision 
of Octopoda he has drawn his characters from the presence or absence of the apparatus 
for resistance, and the aquiferous pores. The Decapoda are arranged by him in two 
groups, according to the modification in the structure of their eyes, to which I have 
before alluded. The first group (J/yopsid@) is divided into three families. In two of 
these, Sepide and Loligide, the characters are taken from the retractile power of the 
tentacular arms, the condition of the internal shell, and the presence or absence of an 
eyelid of a part of the auditory apparatus called by him the auricular crests (erétes 
auriculaires), and of a superior ligament to the funnel; the character of the third 
family (Spzrulide) rests entirely on the internal shell. The second group (Ozgopside) 
also consists of three families, two of which, Loligopside and Teuthide, depend on the 
presence or absence of a lachrymal sinus and the auricular crests, on the funnel being 
or not being provided with an internal valve and ligaments, on the condition of the 
aquiferous pores, and on the shell being with or without air-chambers. The Be/em- 
nitide, the third family, is separated entirely by the character of the internal shell. 
The peculiar modifications in the structure of the eyes among the decapodous 
Cephalopods appear to be of sufficient importance to justify the subdivision of that 
sub-order into the two groups proposed by M. d’Orbigny ; and inasmuch as the adoption 
