in the Ce])halopoda. 113 



young of one species (a Rossia) in the egg, and all these, which 

 belonged to one and the same brood, aj)peaied to nie to be of 

 the same sex, namely females. 



EXPLANATION OF PLATES IL & III. 



Plate IL illustrates tlic position and form of the bectocotylized arm 

 {brachium copidator) m the l)eca])od CejilialoiJoda. 



Fig, 1 . Loligo mvdia, Linn. $ . Head with the two ventral arms, to show 

 that the fourth left arm is papilliferous, and that it has small 

 acetabula in comparison with the right arm. Somewhat enlarged. 



Fig. 2. Loligo Forbesii, 8tp. S • The papilliferous apex of the fourth left 

 arm. Natural size. 



Fig. 3. Loligo guhi, D'Orb. S . The apex of the fourth left arm ; the 

 acetabula are only metamorphosed into papilla: on one side. 

 Double the natural size. 



Fig. 4. Sepioteuthis sepioides, Blainv. c? . The apex of the fourth left arm. 



{Of the natural size, to show the general 

 appearance of this new genus, and the re- 

 markable form of the fourth left arm, on 

 which all the acetabula are deficient. 



£,."■ /.,' >■ This arm double the natural size. 



Fig. 7. Sepia ojicinalis, Linn. S • Ventral arms, to show the peculiar 

 metamorphosis of the fourth left arm, and its difference from the 

 right one. Two-thirds of the natural size. 



Fig. 7'. A small portion of the cutaneous pits on the metamorphosed part, 

 magnified three times. 



Fig. 8. Sepia inennis. Van Hass. A similar portion, to show the peculiarity 

 of the fourth left arm here also. 



Fig. 9. Sepiola Rondeletii, D'Orb. <? . The animal of the natural size, to 

 show this and the preponderance of the first left arm over the 

 rest. 



Fig. 9'. This arm seen from the dorsal surface. 



Fig. 9". The same arm seen from the ventral surface, showing the pecu- 

 liar cutaneous lobe. Magnified three times. 



Fig. 9'". A pair of acetabula from both series on this arm, to show their 

 position. Strongly magnified. 



Plate IIL illustrates the position and form of the bectocotylized arm 

 (brachium copidator), partly in the Decapod genus Rossia, partly in 

 the Octopod Cephalopoda. 



Fig. 1. Rossia Molleri, Stp. <? . The dorsal arms, or the first pair, to show 

 the peculiar elongation of the peduncles of the acetabula on the 

 central parts of the right and left arms, and the strong expansion 

 of the arm-border on the same part. Natural size. 



Fig. 1'. A pair of acetabula, considerably enlarged. 



Fig. 2. Octopus grcenlandicus, Dewh. (= O. arcticus, Prosch.)(?. Of the 

 natural size, to show the position of the bectocotylized third arm 

 in the Octopoda. The four pairs of arms are marked ', ", '", "" ; 

 the letters a, b, c, d, in this and the following figures, always in- 

 dicate the same parts of the arm, namely a, the apical plate; 

 b, b, the muscular cutaneous border, which is white internallv, 



Ann. ^' Mag. N. Hist. Ser. 2. Vol. xx. 8 



