INVERTEBKATE ANIMALS. 73 



muzzle, and by their porcellanous shells smooth or 

 granulated. They are tardy animals resting with their 

 bodies covered up to the eyes in sand, often in deep 

 water. 



The Corystidcs are placed by Dana considerably 

 higher in the series. The external antennae are long 

 and hairy. One species of Corystes inhabits British 

 seas, and is called the Masked-crab. 



Dorippidcs. The two posterior pairs of legs in 

 these degraded-looking crabs are situated on the hinder 

 part of the back, and are adapted for clasping. 

 Estimated number of species : recent, 60 ; British, 6. 



IT Examples of Peltarion, Pseudo-corystes, Perse- 

 phona, Ilia, Ixa, &c. 

 Group 178.— Family CALAPPID^. Nearly every species 

 in this limited group is distinguished by striking pecu- 

 liarities in form or colouring ; but very little seems to 

 be known of the life history of any one of them. The 

 Mediterranean representatives of Calappa are called by 

 the French Crabes Honteux, Modest-crabs, from their 

 habit of hiding their heads and smaller limbs behind 

 their broad - crested nippers, chelce. The armour is 

 certainly strong and very complete, and might be of 

 invaluable service to the wearer if a Calappa had nothing 

 to do but to defend itself from the attacks of enemies ; 

 but how a panoply allowing the limbs but little play 

 can be convenient for the general requirements of crab- 

 life has yet to be discovered, and perhaps may be by 

 the aid of an aquarium. 

 Estimated number of species : recent, 18. 



IT Examples of Matuta, Hepatus, Camara, Orithya 

 mamillaris, &c. 



