142 ALEX.VNDROMEXIA VALIDA. 



elsewhere they are united by strong commissures. In the region of the shell 

 gland this organ is entered, and probably innervated, by several fibres which arise 

 from these ganglia. Posterior to the last of the latero-pedal connectives three 

 or four small branches pass into the muscles about the external reproductive 

 opening. No nerves have ever been followed from this source into the region 

 of the branchial lamellae, and if any are derived from this source they are of 

 verj' small size. 



Alexandromenia valida, sp. nov. 



Four specimens of this species (Plate 3, fig. 3) were collected off the coast 

 of southern California from the following Stations: 2980, 4382, 4389, 4391. 

 The depth ranges from 603-1350 fms. and in every case the bottom was green 

 mud. All the specimens were unattached so that nothing was learned of their 

 habits. The measurements of the largest specimen (Sta. 4389) are as follows: 

 length 32 mm., dorso-ventral diameter of head 3 mm., of cloacal region 3 mm., 

 average diameter of body 3.5 mm. 



The head is not distinct from the body but is characterized by a more 

 pointed appearance than the posterior end, and in all the specimens the borders 

 of the cloacal opening are slightly expanded, exposing, to a slight extent, the 

 gill folds. The atrial opening is relatively small and its forward border is almost 

 level with the front end of the animal. A pedal furrow extends along the ventral 

 surface of the body and posteriorlj- becomes continuous with the cloacal cavity. 

 Anteriorly, for about 1 mm. extent, it expands and allows the escape of the 

 anterior pedal gland secretion (Plate 21, figs. 2, 4) which, in the type, fills the 

 opening and extends posteriorly some distance along the ventral furrow. The 

 general color of the body is light j'ellow. 



A well-developed dorsal sense organ is present, situated in the type about 

 2 mm. from the posterior end of the animal. It is in the form of a shallow pit 

 and is especially conspicuous in surface view on account of the numerous hypo- 

 dermal papillae which surround it. 



The body is surrounded by a cuticle, 0.16 mm. in thickness, which is crowded 

 with innumerable spicules and papillae of large size (Plate 33, fig. 8). The 

 hypodermal layer is concerned almost wholly with the development of these 

 structures, the portion probably responsible for the formation of the cuticle 

 being limited to a few cells packed between the bases of the papillae and develop- 

 ing spines. Everywhere the hypodermal elements are of small size, and though 

 excellently preserved are not favorable for study. 



As just noted the papillae are of enormous size and in a fully developed 



