MALACOSTKACA 7 



word Crustacea. Like that, it was originally adopted to 

 distinguish such creatures as crabs and crawfish and 

 prawns from such others as oysters and clams; not be- 

 cause of the absolute, but because of the comparative 

 softness of their shells. Were reasons wanted for dis- 

 placing the name, they would not be difficult to find. 

 Many of the Malacostraca have shells harder instead of 

 softer than those of some Mollusca. In some Malacostraca 

 the integument has ceased to be of the nature of a shell, 

 a parasitic habit having cancelled the need for such a 

 defence. Moreover, the term suggests a false contrast 

 with the neighbouring sub-class of the Entomostraca, in 

 which as a rule the shells or skin-coverings are still softer. 

 The name Thoracipoda, not open to any of these objec- 

 tions, has been proposed by Dr. Henry Woodward. But 

 against this it may be urged that, by many students of 

 the Crustacea, the w^ord thorax is not admitted as a proper 

 technical term, and among others it is disputed whether 

 the word, if admitted, should apply to three, to seven, to 

 eight, or even to nine, of the crustacean segments. 



Retaining, therefore, the ancient, familiar, and suffi- 

 ciently euphonious word Malacostraca, the subdivisions 

 of this sub-class may next be considered. Two orders 

 have been formed, named respectively the Podophthalma, 

 or stalk-eyed, and Edriophthalma, or sessile-eyed, crusta- 

 ceans. In the former the eyes are mounted upon stalks 

 or peduncles, which are almost invariably movable ; in the 

 latter they are in continuity with the general surface of 

 the head, or, if raised above it, the ocular prominences are 

 unjointed and immovable. That some species in both 

 orders are blind, gives a certain vantage-ground for the 

 disturbers of accepted names to follow their bent. These 

 may also allege that the terms just explained have not 

 been at any time in undisputed possession. The Podoph- 

 thalma have also been called Decapoda, ten-footed, while 

 the Edriophthalma have been called Tetradecapoda, or 

 fourteen-footed, Crustacea. The second of these names 

 has found but little favour, and the first has the dis- 

 advantage that it would apply to some Crustacea that are 



