■§> 233. THE CEPHALOPODA. 271 



2, The Dorsal cartilages are found only with Sepia and Loligo. They 

 are two in number ; the inferior is situated in the neck, and the superior 

 in the mantle at the anterior extremity of the internal shell. The cervical 

 cartilage of Loligo is very long, rhomboid, and pretty massive ; while that 

 of Sepia consists of a thin, semilunar plate, with the cavity directed back- 

 wards. In both genera, its median line has a longitudinal groove ; and in 

 both also, the superior cartilage is only a thin semi-lunar lamella, both 

 extremities of which are extended backwards by a long prolongation. 



3, Those are called Articular cartilages, which, with Argonauta, and 

 the Loligina, are found on each side of the base of the funnel, in the form 

 of long cupels whose cavities receive, when the mantle is closed, the two 

 cartilaginous prominences of its (the mantle's) internal surface.'''' 



4, The Brachial cartilage is found only with Sepia. It is a narrow 

 plate, transversely situated directly in front of the superior border of the 

 cephalic cartilage. It has, anteriorly, three short apophyses for the support 

 of the base of the arms. With the Loligina, there is found in the mantle, 

 at the base of the lateral fins of the body, two other narrow lamellae, — 

 the Fin-cartilages ; these serve as points of insertion of the muscles of the 

 tins, and extend more or less along the sides of the body, taking the form 

 ol' the fins.'*' 



CHAPTER II. 



CUTANEOUS ENVELOPE. 



§ 



233. 



Tlie Cephalopoda are distinguished from the other MoUusca by a wholly 

 }i culiar structure of their skin. The skin is easily detached from the sub- 

 jacent muscular layer, to which it is united by a loose cellular tissue, the 

 iibres of which are interlaced in every direction. The extremely thin 

 epithelium of the skin is lamellated, but never ciliated, with the adult indi- 

 viduals. The Corium is composed of a contractile fibrous tissue, in the 

 meshes of which are contained the remarkable contractile Chromatophoric 

 cells. ^^' These consist of flattened, contractile cavities surrounded by a very 



3 See the figures of Firussac, loc. cit. {Sepia, Cyclop. &c. fig. 212, D. D.), but very short with 



Sepiola,&nA Argonauta). Vfith. Argonauta^tha Sepiola. 



two projections of tlic mantle are round tubercles, 1 For the chromatic cells, see San Giovanni, in 



while with Loligo, Onychoteuthis, and Sepiola, the Giornale enciclojjedico di Nai)oli Ann. XIll. 



tlie.y are two very long longitudinal ridges, to No. 9, or Froriep\'! Not. V. 1823, p. 215, or Ann. 



which corresponds a groove-like excavation iu the d. Sc. Nat. XVI. 1829, p. 308 ; Frenage, Ohsitw. 



two oppositely situated cartilages of the funnel. sur la mobilitt- des taches que I'on remarque sur la 



By means of these articular cartilages, together peau des Calmars, &c., Paris, 1823 ; Delle Chiaje, 



with the two dorsal, when present, the collar-like Memor. &c. IV. 1829, p. 63, and Descriz. I. 1841, 



border of the mantle is exactly fitted about the neck p. 14 ; fVagner, Isis, 1833, p. 159, in fVieg}iiann\s 



of the Cephalopoda. Arch. 1841, I. p. 35, and Icon. zoot. Tab. XXIX. 



* The cartilages of the fins are very long with fig. 8-13, and Harlesn, in }Viegmann''s Arch. 

 Sepia {Schultze, loc. cit. fig. C. D., and Owen, 1846, 1, p. 34, Taf. I.* 



* [§233, note 1.] I have made some careful ob- my subject the common Squid (Lo_ir/fg'Oi7/i'ce6ro«(j). 

 Bervations with the microscope upon the chromatic My results differ somewhat from those of Harlr.ix 

 relations of the skin of the Cephalopoda, selecting for above-mentioned. I found only one kind of pig- 



