The animals of this group are found in shallow seas with muddy bottom, below low-water mark, and feed on organic débris. They have been taken in the Black Sea, Mediterranean, British Channel, and North Sea, and off the Canary Islands (Lanzarote, Porto Pi, Palma di Mallorca). Their size varies from 0.86 mm. × 0.22 mm. in _Echinoderes spinosus_, to 0.14 mm. × 0.03 mm. in _E. kowalevskii_.[291] The BODY is protected by a strong chitinous cuticle distinctly annulated, forming eleven rings, besides a retractile proboscis obscurely divided into two segments at the apex of which the mouth opens. The anus opens on the extreme end of the last segment, which is frequently retracted; the genital pores open right and left of the anus; and the renal pores lie on either side of the back of the ninth segment. The first ring may be undivided, or else distinctly divided into four plates, one dorsal, {237}two latero-ventral, and one ventral. In the remaining segments each ring has only three plates, one dorsal and two ventral, the two latter being sometimes more or less fused in the last or ventral segment. These plates all overlap from before backwards. As the name _Echinoderes_ implies (Thorn-skin), the cuticle is produced into points, bristles, or spines. The last segment frequently bears a large pair of these, which have been compared, on the flimsiest grounds, with the furcal processes of Crustacea and the perforated toes of Rotifers and Gastrotricha. The proboscis when extruded has the form of a truncated cone, obscurely divided into two segments, a ring of strong spines marking the boundary between them, and a second double ring of spines surrounding the apex. The eversion is of the type termed by Lankester pleurembolic or acrecbolic, the sides being first withdrawn, the apex first extruded. As in so many Invertebrata, the epidermis is not separated by boundaries into distinct cells. This layer sends out processes each of which lies in a hollow in the thick cuticle, and perforates it to end in a fine bristle. Minute orange pigment-granules occur at irregular intervals in this hypoderm. The MUSCLES of _Echinoderes_ are simple striated bands. Numerous bands lie within and attached to the body-wall, extending its whole length; paired dorsi-ventral muscles separate the intestine from the reproductive organ on either side, and a complex system effect the movements of the proboscis. ALIMENTARY CANAL.—The pore at the tip of the proboscis leads into a short thin-walled tube, which is rarely evaginated; into the base of this tube projects the short bluntly conical apex of the large ovoid muscular pharynx (or gullet?); this is lined by an epithelial layer of nucleated protoplasm, which secretes a strong cuticle. The stomach is a wide tube, somewhat dilated in each segment between the paired dorsi-ventral muscles, and tapering behind to end in the terminal anus. Four minute glands open at the junction of the pharynx and stomach.