182 MAGILUS. 



pit with a small external ligament. The genera may be thus 

 distinguished. 



1. Lutraria. No lateral teeth, shell gaping. The short 



species constitute the genus Ligula. Fig. 77, 78. 



2. Mactra. Lateral teeth, shell closed. This genus has 

 been divided into Mactra, Mulinia, Schizodesma and Spi- 

 sula, by Mr. Gray. Fig. 79 to 82. 



3. Gnathodon. Teeth serrated, thick, one angular. Fig. 83. 



4. Crassatella. Shell thick, lateral teeth. Fig. 84. 



5. Amphidesma. A distinct external ligament, internal liga- 

 ment oblique. Fig 85. 



6. Erycina. A short tooth on each side of the cartilaginous 

 pit in each valve. Including Mesodesma. Fig. 86. 



7. Ungtjlina. Ligament flat, divided. Fig. 88. 

 MACULATED. (From Macula, a spot.) Spotted or patched. 



This term is applied by conchological writers, to those shells 

 which are coloured in spots or small patches. In the same sense 

 it is also used as a specific name. As for instance, Cytherea 

 maculata, fig. 167, c and Hippopus maculatus, fig. 156. 



MAGAS. Sow. (Mayac, magas, a board, a deck.) Fam. Brachio- 

 poda, Lam. — Deser. Equilateral, inequivalve ; one valve convex, 

 with a triangular area, divided by an angular sinus in the centre ; 

 the other valve flat, with a straight hinge line and two small 

 projections ; a partial longitudinal septum, with appendages 

 attached to the hinge within. Differing from Terebratula in 

 having a triangular disc, and not a circular perforation. Magas 

 pumilus, fig. 299. Fossil in chalk. 



MAGILUS. Montf. Fam. Cricostomata, Bl. Serpulacea, Lam. — 

 Descr. Thick, tubular, irregular, contorted ; rounded above, 

 keeled beneath, free ; apicial extremity convolute, heliciform, 

 ovate or sub-globose; aperture elliptical. — Obs. This shell when 

 in a young state presents the characteristics of a regularly formed 

 spiral univalve, living in holes in madrepores. As the madrepore 

 increases in bulk, the animal gives an eccentric course to the 

 shell, in order to have its aperture even with the surface, and 



