184 PROCEEDINGS OF THE ACADEMY OF [Vol. LXXV 



Spionides sacculata sp. nov. 



Prostomium somewhat T-shaped, without distinct carina; trans- 

 verse limb nearly as long as longitudinal, slightly recurved at 

 lateral ends; longitudinal limb thickened in front where the pro- 

 file is steep, rising to a compressed narrow ridge in the middle 

 and terminating in a narrow, tapering posterior portion, that fades 

 out on the dorsum of somite III, Over the peristomial region a 

 small, erect, conical tentacle arises from this ridge and just anterior 

 to this is one pair of small eyes, one on each side of the ridge. On 

 the ventral side the prostomium is closely united with the peris- 

 tomium which here forms a prominent swollen lip dorsal to which 

 the conspicuous lateral wings project, unite with the parapodia of 

 II behind and, together with the prostomium, enclose the scars of 

 the detached peristomial cirri. 



Setigerous somites short, generally one-fourth or less of width, 

 convex dorsally, venter with a deep neural groove, biannulate, 

 most conspicuously so on the venter, the posterior ring slightly 

 larger and bearing the parapodia. Caudal end and pygidium un- 

 known. 



Parapodia difficult to study on account of crowding and fragility. 

 All are biramous, the two rami crowded closely together and sessile. 

 On anterior segments they occupy the full depth of the lateral 

 face of the segments and extend on to the dorsum across which the 

 postsetal lobes of the notopodia of the first 5 or 6 meet. Neuro- 

 podia more uniform, consisting of a broad ear-like postsetal lamella 

 anterior to which the broad fan-shaped fascicles of capillary setae 

 spread dorsad, laterad and curve caudad, being borne on a broad 

 tubercle lacking a distinct presetal lobe. 



At about XXX (XXIX-XXXII), the interpodal membrane 

 connecting the dorsal borders of successive neuropodia appears and 

 forms a series of conspicuous pockets widely open above and with 

 their bottoms at the level of the ventral surface. After these reach 

 their full development in the middle region the neuropodia gradually 

 decrease in size but undergo no change in form. Neuropodia of 

 this region also become smaller and restricted to the sides of the 

 segments but as far as known (to LXXXV) remain larger than the 

 neuropodia and free from the interpodal membrane. 



Dorsal transverse membrane much less conspicuous than in 

 S. foliata and many other species, reaching from the dorsal border 

 of the notopodium only about half-way to the middle of the dorsum 

 where they fade out. 



Branchiae begin on III, arising from the caudal face of the dorsal 

 border of the notopodia at the root of the post-setal lobe. At 

 first very small, they rapidly increase in size and by XXV, are 

 erect or semi-erect, tapering filaments as long as the dorsal inter- 

 space between the parapodia and arising almost independently of 

 the latter. At about LV, they begin to diminish in size rapidly 

 and within ten segments more, have disappeared. 



