178 ZOOPHYTOLOGY. 



suborbicular, witli a wide sinus in the lower lip ; margin thickened, raised ; 

 a single avicularium (more rarely two) on the side near the mouth. 

 Hab. Mazatlan : on Imp. oUvaceus and unguis. 



This form might easily be confounded with some varieties 

 of L. unicornis^ or L. Ballii (B. M. Cat.) It is distinguished, 

 however, by its reddish colour, and the raised mouth, together 

 with its thickened margin. The single, or sometimes double 

 avicularium, points outwards and upwards, and the mandible 

 is prolonged and acute. This organ is sometimes, but not 

 often absent. 



5. L. adpressa, Busk. (B, M. Cat., p. 82. PI. CIT., fig. 3, 4.) 

 Hab. Mazatlan : on Columhella major, C.fuscata, and Pisania gemmate^ 



not uncommon. Chiloe, 96, fm. Shell ; Darwin. 



The Mazatlan form differs from that from which the former 

 description and figure were taken, in the absence, or indis- 

 tinctness rather, of the radiating grooves. In other respects 

 the two agree very closely. 



6. L. atrofusca, Ey lands, MS. 



Cells elongated, ovate or rhomboidal, bordered with a thin elevated line, 

 surface punctate ; mouth suborbicular, sinuated in the lower lip, toothed 

 on each side. 



Hab. Mazatlan : on Imper. oUvaceus and unguis, and on Anomia. 



General hue blackish ; and even when the cells are more 

 calcareous, and on that account whiter, the dark interstitial 

 line remains very evident. It is quite distinct from L. micul- 

 lata (B. M. Cat., p. 81, Plate 96, fig. 4, 5) which is also of a 

 black colour, and occurs in the Mediterranean. 



7. L. trispinosa, Johnston. (B. M. Cat., p. 70. PI. 85, fig. 1, 2. 



PI. 57, fig. 7.) 

 Hab. Mazatlan : on Imperator ? Britain. 



A single minute specimen only occurred, but this is quite 

 undistinguishable from the British form. 



8. L. rostrata, n. sp. Busk, 1. c, p. 4. 



Cells immersed, surface tuberculous or grauulous ; month immersed, 

 upper margin inconspicuous ; lower lip deeply grooved, armed with a large 

 sessile avicularium, 



Hab. Mazatlan : on Imp. unguis. 



The loAver margin of the mouth, in the mature cells, is 

 deeply grooved in the middle ; and on one side of the groove 

 is a strong, short, blunt spinous process ; and on the other a 

 comparatively large, raised avicularium, which looks towards 

 the sulcus, and whose mandible is acute, and points upwards 

 and outwards. The surface of the cell is often beset with 

 short raised spines or processes ; and these projecting over the 



