TEANSACTIOISTS. 



I. — On the Anatomy and Classification of the Heteropoda. By John Denis 

 Macdonald, R.N., r.R.S., Surgeon of H.M.S. "Icarus." (Plates I., II.) 



(Read SOth January 18G2.) 



Notwithstanding the rapid progress of zoology in other departments, the 

 Heteropoda still remain imperfectly known, if one may form a judgment from 

 the scantiness of definite information respecting them to be found in systematic 

 works. Nearly all the available space is usually occupied with an exposition of 

 the errors and doubts of the great men who gave us the first outlines of the order, 

 while comparatively little is done to improve the subject, or make it intelligible 

 to the student. 



Having had favourable opportunities of examining all the veritable genera of 

 existing Heteropoda^ I have attempted the arrangement of my notes in a con- 

 nected form ; and as they have been taken directly from nature, I am led to hope 

 that some little may be thus added to what may be already known of the parti- 

 cular species investigated.* 



It is usual to divide the Heteropoda into two families, — viz., Firolidoe and 

 A tlantidw j but it appears to me that there is as little difference between Oxp- 

 gyrus and Cardiapoda, as there is between the latter genus and Firoloides, while 

 all three differ sufficiently inter se to warrant their separation into three distinct 

 families, in each of which two well-defined genera may be included ; thus — 



1. Firolidae, Firoloides (Lesueur), Firola (Perou and Les.) 



2. Carinariidse, Cardiapoda (D'Orb.), Carinaria (Lamarck). 



3. Atlantidse Oxy gyrus (Benson), Atlanta (Lesueur). 



* Not having- had the opportunity of consulting many of the original figures of the French 

 naturalists, I have to acknowledge the great advantage I have derived from the study of Mrs Grat's 

 excellent etchings, in helping me to determine species, as also the descriptive letterpress of Dr Gray. 

 Many of the anatomical particulars detailed by me had, of course, been previously observed by others; 

 and though I have not clogged the paper with the separate announcements, dates, and authorities of 

 every addition to our knowledge of Heteropoda, — which, indeed, would be no small task, — I can vouch 

 for it, that all the facts embodied in the text have fallen under my own observation, and they may 

 therefore be regarded either in one sense as original matter, or in another, as confirmation of what 

 had been already made known. 



VOL. XXIII. PART I. A 



