350 Br. H. Woodicard — On Aptyclin& and A2)tycho2)sis, — 



In 1880, Prof. Glaus, " Lehrbuch der Zoologie," writes, "This 

 remarkable form (Nebalia) was for a long time regarded as a 

 Pbyllopod, and in many of its characters it represents a connecting- 

 link between the Phyllopoda and the Malacostraca. The structure 

 and segmentation of the head and thorax resembles that of the 

 Malacostraca, but the terminal region of the abdomen does not 

 present the special form of a caudal plate or telson. 



In Nebalia we probably have to do with an offshoot of the 

 Phyllopod-like ancestors of the Malacostraca, which has persisted 

 to the present time." ^ He adds, " Nebalia is best placed in a special 

 group Leptostraca, between the Entobiostraca and Malacostraca. 

 The Palaeozoic genera Hymenocaris, Peltocaris, etc., would have to be 

 placed in such a group." ^ 



In his " Handbuch der Paleeontologie," Munich, 1885, Prof. Dr. K. 

 A. Zittel adopts Packard's order Phyllooarida, but places it under 

 the Malacostraca, and between the Edriophthalmia and the 

 Merostomata. 



In his article on the Palaeozoic allies of Nebalia, Mr. A. S. Packard, 

 jun., thus sums up the Phyllooarida : " From our total lack of 

 any knowledge of the nature of the limbs of the fossil Phyllo- 

 oarida, we have to be guided solely by analogy, often an uncertain 

 and delusive guide. But in the absence of any evidence to the 

 contrary, there is every reason to suppose that the appendages of the 

 head, thorax, and abdomen were on the type of Nebalia, since there 

 is such a close correspondence in the form of the carapace, rostrum, 

 and abdomen. 



"But whatever may be the differences between the fossil forms 

 represented by Ceratiocaris, etc., they certainly seem to approach 

 Nebalia much nearer than any other known type of Crustacea ; they 

 do not belong to the Decapoda ; they present a vague and general 

 resemblance to the zoea or larva of the Decapods, but no zoea has a 

 telson, though one is developed in a postzoeal stage ; they do not 

 belong to any other Malacostracous type, nor do they belong to 

 any existing Entomostracous type, using those terms in the old 

 sense. No naturalist or palaeontologist has referred them with 

 certainty to the Decapods, or to any other Crustacean type than the 

 Phyllopods. To this type (in the opinion of Metschnikoff and 

 Claus, who have studied them most closely) they certainly do not 

 belong, and thus reasoning by exclusion they either belong to the 

 group of which Nebalia is a type, or they are members of a lost, 

 extinct group. The natural conclusion, in the light of our present 

 knowledge, is, that they are members of the group represented by 

 the existing Nebalia." " The differential characters separating them 

 from the Decapods or any other Malacostracous type are : — 



1. The loosely-attached carapace, the two halves connected by an 

 adductor muscle. 



1 Claus, translated by Sedgwick (Cambridge), p. 448, 8vo., 1884. 



^ Ibid, in a footnote to p. 448. Leptostkaca. — The Leptostraca (Claus) are thus 

 defined: "Crustacea with thin skins, mostly bivalved, and with carapaces under 

 which the body-rings remain separate as free body-segments " (Zittel's Handbuch 

 der Palfeontologie, July, 1885, i. Band, ii. Abth., iv. Lief. p. 655.) 



