250 THE VOYAGE OF H.M.S. CHALLENGER. 



The family Nectalidse is founded by me for the interesting new genus Nectalia 

 (PI. XIII. ), to which probably Sphyrophysa of L. Agassiz (36) is closely allied. They 

 have in general a similar organisation to the well-known Discolabidse {Physophora), but 

 differ from them essentially in the possession of a large protecting corona of cartilaginous 

 bracts at the apex of the siphosome. 



Nectosome and Siphosome. — The corm of the Nectalidse is composed of a long columnar 

 nectosome and a flat coroniform siphosome. The trunk of the nectosome is a slender 

 vertical tubule, and bears either two opposite or four cruciate rows of nectophores ; and 

 at the apex a pneumatophore with four radial chambers. The trunk of the siphosome 

 is shortened, vesicular, and horizontally expanded in form of a spiral bladder, to which 

 are attached the following parts : — Uppermost a corona of bracts, beyond it a corona of 

 palpons or cystons, below a bunch of siphons and tentacles, and at the distal base a 

 group of clustered gonophores. Probably these polymorphous persons and organs are 

 arranged regularly in ordinate cormidia, as in Pliysophora ; but in the single specimen 

 observed by me it was impossible to make out this metameric arrangement with full 

 certainty. I suppose, however, that each nectophore belonged originally to a cormidium, 

 which was composed of the following parts : One bract, one palpon, one siphon with a 

 tentacle, and two gonodendra, a male and a female. 



Pneumatophore (PL XIII. figs. 1-3, p, 4). — The float, placed at the apex of the 

 siphosome, is in Nectalia pyriform, and exhibits four vertical radial septa, which connect 

 the outer with the inner wall ; the cavity of the pneumatosac is divided by them into 

 four large radial pouches. An opening at the apex of the pneumatocyst was not visible, 

 but there seems to be one at its base (just as in Physophora). 



Nectophores (figs. 1, n, 5-8). — The column of nectocalyces in Nectalia is composed of 

 two opposite longitudinal rows, in Sphyrophysa of four cruciate rows ; the former bears 

 therefore the same relation to the latter as in the following family Physophora does to 

 Discolabe. The nectophores are similar in form and structure to those of many other 

 Physonectse, and they embrace the trunk of the siphosome so fully by two apical horns 

 or wings, fitting in the space between two obliquely opposite nectophores, that the struc- 

 ture of the nectosome becomes very solid. The subumbrella of the nectophores has a 

 strong muscle-plate, and renders possible a very rapid movement of the swimming corm. 

 The velocity of the swimming Nectalia is much greater than that of most other 

 Physonectse, and comparable to that of Diphyes, Sagitta, and Loligo. 



Bracts (figs. 1, 9-12). — The prominent character of the family Nectalidse is found 

 in the corona of bracts, which is attached to the apex of the siphosome immediately 

 beyond the base of the nectosome ; it is similar to that of the Anthophysidse, and is 

 wanting in the Discolabidse, which are otherwise nearly related. The bracts of Nectalia 

 are strong cartilaginous covering scales of a peculiar form and differentiation, especially 

 described below. They are raised and subhorizontally expanded in the quietly-floating 



