STATE GEOLOGIST. 85 



The Pectostraea (including Phizocephala and cirripeda (barnacles) have been 

 assigned a place among the Entomostraca from facts learned regarding their 

 development. These crustaceans have been tossed from one division to another 

 till they ought, it would seem, to find a permanent resting place. First consid- 

 ered mollusks, they have now taken their position among the lower crustaceans. 

 These creatures, which are at maturity firmly cemented to foreign bodies, and are 

 inclosed in a hard shell-like test have, in their earlier stages, forms resembling 

 the "Nauplis" stage of Cylops (see plate III,) and also a stage resembling the 

 mature Cypris. 



It is now known that, as Huxley expresses it, ' ' the barnacle is a crustacean 

 fixed by its head and kicking its food into its mouth." The attachment of the 

 head finds a parallel in the genus Sida (see beyond), which contains animals that 

 can attach themselves at will to bodies by a sucker- hke disk on the head, corres- 

 ponding to the pedicle of the barnacles. As the barnacles and epizoa have not 

 been observed no further mention will be made of them in this connection. 



The following table from Huxley's Anatomy of Invertebrates will perhaps be 

 useful for reference. 



(Articulates or) 



ARTHROPODA. 

 , I. 



Without manducatory appendages (Gnathites) 

 Trilobata. Tardigrada ( ?) Pentastomida( ?) 



XL 



With pediform gnathites. 

 Merostomata, Arachnida. Peripatidea. 



III. 



With maxilliform gnathites. 

 Entomostraca. Myriapoda. 



Malacostraca. Insecta. 



Water- breathers. Air-breathers. 



For the most part. 



The extent of the Entomostraca has been outlined above, and the Malacostraca 

 includes the remainder of the crustaceans, viz : those included by Dana under 

 Podophthalmia and the order Choristopoda of Edriophthalmia, thus embracing 

 crabs, shrimps and all the higher crustaceans, whose body consists (almost always) 

 of twenty segments (somnites) of which six constitute the head, and bear, respect- 

 ively, the eyes, superior antennae, inferior antennae, mandibles, and two pair of 

 maxillae. Of the remaining somnites eight pertain to the thorax, and carrj' the 

 foot jaws and walking hmbs, while six are abdominal and bear swimming limbs. 

 These higher forms do not go through the Nauplius stage in their development, 

 as do the Entomostraca. 



