210 AllACHNIDES. 



FAMILY II. 

 PYCNOGONIDES. 



The trunk, in this family, is composed of four segments, 

 occupying nearly the whole length of the body and terminated 

 at each extremity by a tubular joint, the anterior of which is 

 the largest, sometimes simple, and sometimes accompanied by 

 cheliccrai and palpi, or only one kind of these organs, that 

 constitutes the mouth(l ). There arc eight legs in both sexes, 

 formed for running, but the female is furnished with two ad- 

 ditional false ones, placed near the two anterior, and solely 

 destined to carry her eggs. 



The Pycnogonides are marine animals(2), analogous either 

 to the Cyami and the Caprellse, or to the Arachnides of the 

 genus Phalangium, where Linnaeus placed them. Their body 

 is commonly linear, with very long legs, composed of eight or 

 nine joints, terminated by two unequal hooks which appear 

 to form but one, and the smallest of which is cleft. The first 

 segment of the body, which replaces the head and mouth, 

 forms a projecting tube, cylindrical or in the form of a trun- 

 cated cone, with a triangular aperture at its extremity. The 

 chelicersB "and palpi are placed at its base. The former are 

 cylindrical or linear, simply prehensile, and composed of two 

 joints the last of which is a forceps, the inferior finger or the 

 one that is fixed being sometimes shorter than the other. 

 The palpi are filiform, and consist of five or nine joints, with 

 a terminal hook. Each of the following segments, the last 

 excepted, bears a pair of legs(3); but the first, or the one arti- 



(1) On the siphon of a large species of Phoxichilus brought from the Cape of 

 Good Hope by the late M. Delalande, I observed longitudinal sutures, so that it 

 appears to me to be composed of the labrum, ligula, and two jaws, all soldered 

 together. In this case the palpi belong to the jaws. 



(2) According to Savigny they form the transition from the Arachnides to the 

 Crustacea. We place them here, but with some hesitation. 



(3) M. Milne Edwards, who has investigated the anatomy of these animals on 

 the living subject, has told me that in the interior of these organs he observed 



