412 THE INDIAN UMBKELLA. 



is flat, blunt in front, and the eyes are deeply sunk in the tissues. The shell is cylindrical 

 and mostly smooth, and the aperture is narrow. 



JUST below the head of the aplustrum a curious animal is seen, represented as it 

 appears when crawling over the rocks. This is the BOATMAN'S SHELL, a specimen of 

 a very small genus, containing only five species, but yet represented in England. It is 

 a sand-loving creature, mostly remaining in a rather considerable depth, and being found 

 in fifty fathoms of water. This animal has no eyes ; and although the side lobes are 

 turned up, and are very large, they do not envelop the shell. In order to show the 

 formation of the shell, an empty specimen is given just below the living animal. 



WE now come to another family, in which the shell is never visible, being either very 

 small and covered by the mantle, or wholly wanting, and in some instances being 

 translucent and flexible as horn. The common SEA HAKE (aplysia dcpilans] is a well- 

 known example of this curious genus, which has given its name to the entire family. 

 The Sea Hares possess the power of throwing out at will a rather large amount of 

 a peculiar coloured fluid, mostly of a deep violet, which is secreted by part of the mantle. 

 This habit formerly caused the Sea Hare to be held in great dread, the popular opinion 

 attributing to the violet fluid the most virulent properties, such as staining the skin 

 indelibly with the purple dye, injuring its texture like strong caustic, and causing the 

 hair to fall off. In allusion to the last-mentioned idea, the animal has received its specific 

 title of depilans. 



WE will now briefly examine a few of the more remarkable species. 



At the bottom of the engraving is seen an oddly-shaped creature, looking as if it 

 were made of some rough membrane covered with little projections, and tacked loosely 

 Dver an egg-shaped centre. This is the DOLABELLA, or HATCHET- SHELL, so called on 

 account of the form assumed by the shell, which is, however, so entirely hidden under 

 the softer parts that it is not visible until the lobes have been put aside. 



In order to show its peculiar shape, one of the shells is represented as it appears when 

 separated from the animal. As may be seen, it is small in proportion to the size of the 

 creature which formed it, and as it is attached only to the hinder part of the body, it is 

 of little use in protecting the soft parts from injury. In colour the shell is pure shining 

 white and pearly ; its substance is veiy thick, and it is covered with a tough membrane, 

 technically called the epidermis. The colour of the animal is dull olive-green. 



OUK last example of this family is the animal which is shown on the upper right- 

 hand corner of the illustration, and represented in the act of swimming, for the purpose 

 of showing the manner in which the side lobes can be used as fins, and employed 

 in urging the animal through the water. This creature is called LOBIGEE, or Lobe- 

 bearer, in consequence of the rounded and flattened lobes that project from each side of 

 the body, much like the four wings of a butterfly. The tentacles are also flattened 

 and rather oval, and the eyes are very small and set on the sides of the head without any 

 footstalks. The foot is small, and the hinder part of the body is lengthened and pointed 

 so as to resemble a tail. The shell is small, oval, transparent, flexible, and set on the 

 body so as to act as a shield to the plume-like gills. This species is found on the coasts 

 of Sicily. 



THERE is a curious animal belonging to the next family of molluscs, called, from the 

 mode in which the shell is carried, the INDIAN UMBRELLA. In this creature the body is 

 large, roundish, and covered with tubercles, and in shape something resembling a great 

 limpet; while the flat, white, pearly shell is perched horizontally on the very middle of 

 the back, just like an Eastern umbrella held over the palanquin of some great potentate.' 

 The colour of the animal is dull ochreous yellow. 



WE now arrive at a very remarkable series of molluscs which have been separated 

 by systematic naturalists into' a distinct section, appropriately called Nudibranchid;e, or 

 }laked-gilled Molluscs, because their gills are always external and placed on the back or 



