170 SYSTEMATIC ARRANGEMENT 



horizontal, compact, rather short, blunt strands : the artery and 

 branchial vein are easily observed ; the plume gradually curves and 

 tapers from its origin to a pointed termination, and is of the palest 

 uniform hyaline drab ; it may often be seen exserted and vibrating 

 like a tentaculum in all directions ; the anus is under the plume. 



The foot serves as a nidus for the membranous vesicular envelope 

 when the young are expelled from the matrix, and when the embryos 

 have left it is discharged, as in lanthina. — Clark, Moll. 263. 



Head of Tectum parva large, with a sharp edge in front and on the 



sides. Tentacles subulate. Eyes ? Foot simple, without any 



lines. Mantle edge simple, under side smooth. Gill triangular, end 

 free? 



Fig. 91. — Teeth of Tectura parva. 



The teeth of Tectura parva are square, entire, in a diagonal 

 series ; tips conical (fig. 91). 



The teeth of Tectura testudinalis are square, with the anterior 

 outer angle retuse and produced ; teeth two on each side, the anterior 

 long, slender, furnished with a hook at the inner angle ; posterior 

 almost transverse, with a double cutting edge, the inner much the 

 larger and subtriangular. 



The mantle of Tectura scutum (Lottia punctata. Gray) is thin, 

 with a rounded thickened edge, without any appearance of beards in 

 the specimen preserved in spirits. Gills triangular, elongate, from 

 the left side of the hinder part of the gill-cavity, free the whole of 

 its length, and formed of regular transverse laminae united by a con- 

 tinuous margin on each side. 



The lingual membrane of Tectura Wiltoni, from the Cape of Good 

 Hope, is elongate, linear, dark brown, with a transverse paler line 

 between each set of teeth. Teeth 3 ' 3, brown ; apex opake black, in 

 oblique lines, conical, acute, curved ; the inner close together, curved 

 forwards ; the middle and outer lateral curved outwards ; the outer 

 lateral bifid, as if formed of two cones. 



The teeth of Tectura apicina, also from the Cape of Good Hope, 

 are similar in all respects to T. Wiltoni, but the middle lateral teeth 

 are smaller and slenderer above ; the two outer lateral are three- 

 lobed, the two apical lobes being nearly equal, and the one at the 

 upper part of the base smaller. 



The lingual membrane of Tectura ?, from Magellan Straits, 



is elongate, linear, narrow, brown. Teeth 2 '2, brown; apex conical, 

 curved, claw-like, acute, opake black ; inner close together, with the 

 hook bent outwards ; apex when worn truncated ; outer far apart, 

 with the hook bent inwards towards the centre, when worn truncated. 



The lingual membrane of Tectum, no. 266, is linear, very narrow, 



