STERXASPIS FOSSOR. 405 



filamentous branchiae arising from a plate or shield thi-ough perforations in 

 which they pass. 



No parapodial processes. Each of somites II, III, and IV with a long row 

 of stout acicular setae, or spines, on each side; the distance between the ends of 

 the lateral series above and below increases from somite II to somite IV. 



No setae on somites V, VI, and VII. Setae of somites VIII to XV, inclusive, 

 are abortive, ordinarily not emerging through the cuticle. The remaining somites 

 have fasciae of long sunple setae which radiate from the edges of the shield, 

 there being (at least in S. scutata) seventeen pairs of these fasciae. 



The nepliridia are in the form of a single pair of tubercles provided with 

 small, ciliated, internal funnels and nephrostomes, but without external openings. 

 The gonads are represented by a trilobed sac with two ducts, each of which opens 

 at the tip of a slender genital process at the anterior ventral edge of somite 

 VIII (Goodi-ich, Op. cit., p. 233, pi. 15, fig. 1, etc.). The alimentary canal is 

 conspicuously coiled. The pharynx is a conspicuous bulbous division followed 

 by a slender oesophagus. The stomach is much thicker and dilatable, and is 

 followed by a slender intestine which terminates in an expanded rectum. A 

 remarkably long, two-branched proboscis, which is easily lost, has been described 

 for S. spinosus (Sluiter, Naturk. tijds. Neederl. Indie, 1882, 41) and may be 

 present in Ufe in all. 



These worms have various structural characters suggesting the Echiuroidea, 

 with which group they have often been connected, e.g., by Carus, Gegenbaiu-, 

 and Huxley. In fact, scutata, the first and best known species, was placed by 

 Ranzani in the genus Thalassema; and when Otto made a new genus for it he 

 sought to recall the supposed resemblance by changing the specific name to 

 thalassemoides. Otto, Meckel, and Cuvier regarded Sternaspis as an echino- 

 derm. 



The species of Sternaspis, the only genus thus far known, live mostly on 

 muddy bottoms, at depths between 15 and 628 fms. S. major, a new species 

 (p. 406), having been taken at the latter depth. 



Sternaspis Otto. 



Nova acta Acad. Caes. Leop. nat. curios., 1821, 10, pt. 2, p. 619. 



Sternaspis fossor Stimpson. 



Invertb. Grand Manan, 1853, p. 29, pi. 2, fig. 19; Verrill, Invertb. Vineyard Sound, 1873, p. 507, 606, 

 pi. 14, fig. 74; Levinsen, Ofvers. Nordiske Annulata, 1883, pt. 2, p. 214; M.-uienzelleb, Ann. 

 Naturhist. mus. Wien, 1890, 5, p. 5, pi. 5, fig. 4-4b, 5, oa, 7; Augener, Bull. M. C. Z., 1906, 

 43, p. 191. 



