EXPLANATION OF PLATK 45. 71 



the circular lines on the surface of its horny mem- 

 brane dy 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. (Ori- 

 ginal.) 



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

 tially surrounded by brilliant nacre. In no one of 

 the specimens represented in PI. 44" is the least 

 trace of the calcareous sheath of the Belemnite pre- 

 served. See V. I. p. 376, Note. (Original.) 



Plate 45.* V. I. p. 392 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 cor- 

 responding parts of different animals, a. the shield ; a. lateral 

 portion of the shield ; b. the eye ; b\ eye magnified ; b". frontal 

 eyes; c. the back; d. the tail ; e. branchiae. 



