EXPLANATION OF PLATE 45. 71 



the circular lines on the surface of its horny mem- 

 brane d, are lines of growth. (Original.) 



Fig. 3. Belemno-sepia from the Lias at Lyme, in the 

 Oxford Museum ; the Ink-bag is preserved entire 

 within the anterior conical sheath e. e. e. ; the 

 greater part of this sheath is highly nacreous, in a 

 few places (d.) it is horny. (Original.) 



Fig. 4. Large Ink-bag from the Lias at Lyme, in the 

 collection of Mrs. Murchison, bearing on its surface 

 undulating lines of growth similar to those on the 

 surface of Fig. 1. The Ink is exposed at c. c. ; in 

 other parts it is surrounded by the sheath, e. e. e. 

 Nearly one-half of this sheath retains the appear- 

 ance of horn, whilst the other half is highly na- 

 creous. This interchange of condition, from horn 

 to brilliant nacre, occurs in almost every specimen 

 from the Lias at Lyme, in which the Ink-bag is 

 accompanied only by the flexible anterior sheath, 

 and the calcareous sheath has perished. (Original.) 



Figs. 5. 6. 7. 8. Ink-bags from the Lias at Lyme, partially 

 surrounded by brilliant nacre. In no one of the spe- 

 cimens represented in PI. 44" is the least trace of the 

 calcareous sheath of the Belemnite preserved. See 

 V. I. p. 283, Note. (Original.) 



Plate 45.* V. I. p. 296 et seq. 



Fig. 1. Limulus Americanus (Leach,) a young speci- 

 men from Honduras, one-third of nat. size. b'. 

 Right compound Eye magnified, b". Two single 



* The following letters are applied in PI. 45 and PI. 46, to corre- 

 sponding parts of different animals, a. the shield ; a', lateral portion 

 of the shield ; b. the eye ; V. eye magnified ; b". frontal eyes ; c. the 

 back ; d. the tail ; e. branchiae. 



