326 Recherches sur les Poissons Fossiles. 



just as a broad short scale would appear more long than high, 

 from the superior and inferior border being much concealed 

 by the imbrication before and behind. It is also necessary 

 to distinguish the different modes of imbrication : the most 

 simple is that where the scales of each transverse series 

 have simple joinings by the superior and inferior borders, 

 without being overlapped in their anterior part by the middle 

 of the posterior border of the scales of the series which pre- 

 cede. We observe this disposition in nearly all the Ga- 

 noids, with this difference only, that sometimes the scales 

 of the consecutive series alternate the one with the other, 

 so that the superior and inferior borders of an anterior 

 series correspond to the middle of the scale of the following 

 series, for example, in the anterior parts of the trunk of 

 the Lepidosteus, t. xi. f. 1 and f. 3, so much of the borders 

 are placed in a line with one another, as for instance in the 

 posterior part of the trunk of the Lepidostes, f. 6, or rather 

 they are brought but little over towards the superior or inferior 

 part of the following scale, as in the Polypterus, f. 2. Some- 

 times the upper and lower borders of two scales appear to 

 have simple juxtaposition, and are applied one against ano- 

 ther to their square sides, for example t. xi. f. 6, 7, 8, or rather 

 they have their edges cut so as to fit diagonally between the 

 superior and inferior borders in a manner to afford the most 

 intimate union in their partial superposition; for example, 

 t. xi. f. 3, 4, 5, or lastly, the superior border of one scale is 

 provided with a very salient hook or crochet, which corres- 

 ponds to a hollow in the lower border of the superior scale 

 to which it is fixed, such are the scales, fig. 9, 10, 11, 12, 

 and 13. 



Another mode of imbrication, is that where the scales do 

 not overlap by means of anterior and posterior series, but 

 yet wherein each series, each superior scale covers with its 

 interior border, a portion more or less of the superior 

 border of the inferior scale. Generally, when the imbri- 



