344 THE GOOSE-BILL LAMP-SHELL. 



The ORDER THECOSOMATA is a division embracing the Hyaleas and Gleodoras. The 

 family Cymbulida includes some comparatively large species, which secrete peculiar looking 

 shells. They are slipper-shaped, and very much like a mass of jelly, thick, transparent, and 

 flexible. Species are Cymbulia and Tiedemania. 



The ORDER GYMNOSTOMA embraces the Naked Pteropods. Glione is a more common 

 genus. C. borealis is the familiar Arctic form which is seen in vast patches on the ocean. 

 This, with the Limacina, a member of the preceding order, forms the principal food of the 

 whalebone whale of the North Atlantic. Clione papilionacea is found in our waters as 

 far south as New York. Its. resemblance to a butterfly gives it the specific name. 



BRACHIOPODA AND CONCHIFERA. 



As group after group of mollusks passes before our notice, each seems to be more 

 extraordinary than its predecessor, and to present us with stranger and more unex- 

 pected forms. 



The mollusks of the next group are the first of the bivalves, but stand alone in many par- 

 ticulars, and evidently form a transition between the gasteropoda and the ordinary bivalves. 

 They are all inhabitants of the sea, and, when adult, are found attached to rocks, conil 

 branches, and even other shells ; but in their earlier stages are apparently able to swim freely 

 through the water, as is the case with many other mollusks. 



In the ordinary bivalves, the two shells correspond with the right and left side of the 

 animal ; but in the Brachiopoda, as these creatures are called, the one covers the upper and 

 the other the lower portion, and are called accordingly the dorsal and ventral valves. Of 

 these, the former is smaller than its companion, to which it is jointed by means of certain 

 interior sockets, which receive corresponding hooks in the ventral valve, and lock them 

 together so tightly, that they cannot be separated witnout something being broken. The 

 ventral valve is large, and is marked by a decided beak, not unlike the bill of a parrot. In 

 most instances the beak is perforated with a round hole, through which passes the peculiar 

 organ by which the animal attaches itself to the substance on which it rests ; and when this 

 is not the case, the hooked beak itself answers that purpose. 



In the interior is a rather complicated internal skeleton. The food is obtained in a singu- 

 lar manner. The animal is furnished with a pair of rather long arms, covered with vibrating 

 fibres or cilia, and by means of the constant action of the cilia a current is caused, which 

 drives a continual stream over the mouth, and enables the animal to seize the minute animals 

 that dwell in the sea and are distributed throughout the waters. 



WE will now proceed to the examination of our selected examples of these curious 

 mollusks. 



The genus Terebratula is the first to mention. This name is derive from a Latin word 

 signifying a wimble, and is given to the animal in allusion to the round hole which perforates 

 the beak. The popular name of LAMP-SHELL also refers to the same aperture, because it looks 

 like the round hole through which the wick of an ancient lamp is drawn. The structure 

 of the shell itself is very curious, being made up of innumerable flattened prisms laid side by 

 side and arranged in a slightly oblique position, so that their ends project over each other, 

 something like the slates in a house-roof. The substance of the shell is also perforated by 

 multitudes of very minute circular apertures. 



Next comes the PARROT-BILL LAMP-SHELL, so-called from the shape of the beak, which is 

 long and hooked in a manner which much resembles the beak of the bird whose name it bears. 

 The color of this species is black. 



Our last example of these remarkable mollusks is the GOOSE-BILL LAMP-SHELL. All the 

 members of the family to which this animal belongs are known by the long and comparatively 

 narrow valves, and the footstalk which attaches them to the rocks, and which passes from 



