LEPTOSTRACA. 455 



name Peracarida * for a group containing all Eumalacostraca 

 possessing a brood pouch, and in this the Holotropha are included, 

 while the Hemitropha are united with the Decapoda in the 

 group of the ' ; Eucarida." The division, Schizopoda, would, 

 on this arrangement, cease to exist. 



While admitting that there is much to be said in favour of the 

 course proposed, it appears preferable, in the present work, 

 to retain the group Schizopoda. Zoologists are far from being 

 agreed on the change, and it was strongly resisted by Claus. f 

 Were it adopted the relations of several of the groups of the 

 Malacostraca would still remain highly debatable, and especially 

 that of Anaspides to the others. 



The Malacostraca fall into two divisions, the Leptostraca 

 and the Eumalacostraca. A tabular view of the divisions of 

 the Malacostraca will be found in the Table of Contents. 



Division 1 (and Order). LEPTOSTRACA4 



Crustacea with a bivalve shell covering the head and middle 

 portion of the body, and a movable head-plate attached in front : 

 with eight well-defined thoracic, segments bearing appendages similar 

 to one another, and eight abdominal segments, of which the anterior 

 six bear appendages. The terminal segment carries a caudal fork. 



The Leptostraca are small shrimp-like creatures, living in the 

 sea in different parts of the world, from shallow water down to 

 depths of over 2,000 fathoms. 



Among the various groups of Crustacea now living the genus 





a pouch. 



A piece of evidence against the breaking up of the Schizopoda is 

 contained in the work by Keeble and Gamble, above cited, who find that the 

 colour pattern which is permanent in the holotrophous Macromysis is the 

 larval pattern of shrimps. It is, of course, possible that this is a widely 

 distributed pattern in the lower Malacostraca, but in the present state of 

 our knowledge the fact favours the retention of the group Schizopoda. 



{ Besides the works of Leach, Latreille and M. Edwards, compare 

 Claus, Crustaceensystem, I.e. Wien, 1876. A. S. Packard, The Order 

 Phyllocarida and its systematic position. A monograph of the Phyllopod 

 Crustacea, etc., Boston, 1883. G. O. Sars, Report on the Phyllocarida, 

 Challenger Reports, 56, vol. xix, 1887. Claus, Ueber den Organismus der 

 Nebaliden und die systematische Stellung der Leptostraken, Arbeiten 

 aus dem Zool. Inst. d. Univ. Wien, Tom. viii, 1888. J. Thiele, Die Lepto- 

 straken Wiss. Ergeb. d. Deutsch, Tiefsee Exped. (Valdivia), Bd. ,viii. 

 Liefn. 1, 1904. 0ber die Leptostraken der deutschen Siidpolar-expedition, 

 1901-3. Deutsch. Sitdpolar- expedition, Bd. ix, Heft. 1, Berlin, 1905. 



