1383.] PEOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 401 



Vol. Till, I¥o. 36. Waisihm^toii, D. C. S ept. 14 , 1885. 



The margin of tlii.s surface ({intero-lateral) is therefore made up of 

 bounding lines of unequal length. As the outlines of the curved lines 

 which form the sides opposite those of the anterior rectangle are some- 

 what distorted, it is not possible to determine whether they are simply- 

 curved or double, composed of two ridges forming at their junction an 

 obtuse angle. The latter condition exists in A. trigona as described by 

 Huxley. 



Seen from the posterior face (Fig. 2) the anterior nectocalyx has a 

 cubical or spherical projection in the middle, which is bounded by a 

 triangular plane surface, the sides being at first almost parallel and 

 then bending together below in a short angle just above the entrance 

 into a depression (y.), into which fits the anterior extremity of the pos- 

 terior nectocalyx. In the specimens i3reserved in alcohol the posterior 

 lateral planes (pi.) are composed of two parts, one of which is parallel 

 with the triangular plane, the other at right angles to it. The upper 

 posterior plane (np.) is hexagonal, one side formed of the upper side 

 of the posterior triangle. The two adjacent sides are formed by the 

 bounding lines of the posterolateral planes just mentioned and a part 

 of the anterolateral planes with the uj^per bounding line of the posterior 

 face. 



The posterior lateral planes {pi.) are polygonal with bounding lines 

 of unequal length. The outer wall of these planes is the margin of the 

 anterior nectocalyx, and the lower the ridge which forms a division be- 

 tween the lateral plane and the opening into the cavity, into which the 

 anterior end of the posterior nectocalyx fits. The outer border of the 

 lateral planes is toothed at the lower rim. 



The great width of the antero-lateral {al.) and posterior lateral (pi.) 

 planes imi)arts to the anterior nectocalyx a great breadth, and in alcohol 

 we seem to have two lateral wings. How much of the shrinkage which 

 causes this modification is due to the alcohol cannot now be determined. 

 The thickness in the lateral walls between the middle line of the necto- 

 calyx and the margin of the faces (anterior and p^terior), or the crest 

 of the bounding angle, is much greater than that which passes from 

 the same line through either somatocyst or bell cavity. The same is 

 also true in A. trigotia described by Huxley. 



In a bottle with the anterior nectocalyx are fragments which are 

 identified as the posterior nectoc^lyces. These, however, are not fast- 

 ened to the former, yet there is no doubt that they belong to the same 

 genus. 



POSTERIOR NECTOCALYX. 



The posterior nectocalyx, although shrunken from its former pyram- 

 idal form, is in a good condition for study. Its whole length is 20™'". 

 The outer suriace is crossed by three longitudinal crests, which extend 

 Troo. Nat. Mus. 8o-^r— 26 



