Zoological Society. ■ 129 



tremity is more inflected and more obtuse in the male ; the oral ex- 

 tremity in both is obtuse and truncate. 



" The surface of the body appears to the naked eye to be mi- 

 nutely striated transversely: it is variegated by the white genital, 

 and amber-coloured digestive tubes appearing through the transparent 

 integument. When* examined with a lens of half-inch focus, the 

 anterior two-thirds of the body are seen to be covered with circular 

 series of minute reflected spines, which, viewed with a still higher 

 power, present three distinct points, one large one in the middle and 

 two small lateral ones. 



" The mouth is surrounded by a tumid circular lip armed with six 

 or seven circular rows of well-developed spinous processes of a simi- 

 lar complex structure to those on the body. The oral orifice itself 

 presents the form of a vertical elliptical fissure, bounded on each 

 side by a jaw-like membranous fold or process, the anterior margin 

 of which is produced in the form of three straight horny points or 

 processes, directed forwards. These lateral processes can be pro- 

 truded beyond the circular lip by compressing the smooth spineless 

 skin behind the latter; and the elasticity of the structure causes them 

 to be again retracted on remitting the pressure. 



" The vulva is situated at the junction of the middle and posterior 

 thirds of the body ; the anus in the female is in the form of a trans- 

 verse semilunar fissure immediately behind the obtuse posterior apex, 

 and on the concave side of the inflection. 



" The anus of the male, from the anterior part of which a single 

 slightly-curved intromittent spiculum is protruded, is surrounded by 

 eight distinct pointed papilla, three of which are placed in a vertical 

 row on each side, and two smaller ones at the lower boundary of 

 the common opening to the rectum and male gland. 



" On comparing this Nematoid worm with those already described, 

 it approaches most nearly to some species which are referred by 

 Rudolphi to the genus Strongylus, as the Strongylus trigonocephaly, 

 R., (Hist. Entoz. ii. pi. I. p. 231.,) in which species the 'Bursa maris 

 subglobosa, biloba, multiradiata,' presents an approximation to the 

 structure of the external male organs above described, in which the 

 eight tubercles surround the opening somewhat after the manner of 

 rays. But on pursuing the comparison we find that here the re- 

 semblance ceases : there is no subglobose bilobed sheath to the in- 

 tromittent organ in the species here described ; the head is sur- 

 rounded by a circular instead of a trigonal lip ; the Strong, trigono- 

 cephalus is placed by Rudolphi in the section c, ore nudo, while 

 the armature of the mouth, in the present species, is so remarkable, 

 as to induce me to regard it as the type of a new genus, which I pro- 

 pose to denominate Gfiathostoma*. 



" Gen. Char. Corpus teres, elasticum, utrinque attenuatum. Caput 

 unilabiatum, labio circulari tumido integro ; os emissile, processibua 

 corneis maxilliformibus duobus lateralibus denticulatis. Genitale 

 masculum spiculum simplex, ad basin papillis circumdatum. 



• yv*6o; maxilla, irrouec Of. 



Third Series. Vol. 11. No. 65. Supplement, July 1837- S 



