Naviriilacea.l rNFUSrtRiAT, animat.cut.es. 4S3 



(navicular bodies) scattered single, or in pairs, with a circular spot at 

 the angles. 



"Fi'ond extremely tender, it tapers at the base and expands 

 upwards into a lanceolate or obovate form. I could detect neither 

 striae nor puncta in the frustulcs, which in the front view are nearly 

 quadrate, and are rarely twice as long as broad ; in the lateral view 

 they are narrow linear, with roimded ends ; as they do not appear to 

 be siliceous, it is probable that dried specimens become in that view 

 somewhat narrower than they are when recent ; a fact, which I have 

 noticed in some genera of this order, whose frustules cannot, without 

 injury, be submitted to the action of nitric acid. 



" Bichieia differs from Schizonema by its flat fronds and scattered 

 finistules. (Ann. Nat. Hist. 1858, v. 1.) 



DicKTEiA Ulvoides. — Of a pale purplish-white colour ; olive when 

 dried ; stalk very slender, capillary, short, fi-ond oblong, irregularly 

 lobed, or crenate ; tapering gradually to its base; navicular bodies rather 

 broad, oblong, in pairs, angles obtuse, and apices truncate. Length 

 of navicular l-720th., of frond one-and-a-half inch. Found on the 

 Coast ofAberdeen, in the Spring. (P. 24, f. 31, a, h, c, d, and e.) 



"D. pinnata. — Found spaiingly, pinnate, all the divisions 

 lanceolate. 



"Fronds olive-brown, becoming greener when dried, one to two 

 inches high, lanceolate, irregularly pinnate ; the pinna? lanceolate 

 and alternate ; the margins, both of the primary portions and of the 

 divisions, are uneven and minutely lancinated. The fr'ustules are 

 like those of the preceding species, from which it differs by its darker 

 colour, divided frond, and more tapering extremities, and in being an 

 autumnal, not a vernal species. In shallow marine pools, Torquay." 



D. Danseii (Thwaites, Ann. Nat. 1848.) — Frond gelatinous, in- 

 definite, mammillose ; naviculse oval, striated. (P. 24, f. 30, a, b.) 



The frustules of this species are siliceous and of an oval form, with 

 a linear space, on either side of the centi-al band, striated. This 

 beautiful new species is extremely interesting, as illustrating the real 

 structure of Dickieia. Each fi-ustule developes around itself a 

 definite amount of gelatine, so that at each repetition of fissiparoua 

 division additions are made to the amount of gelatine of the frond 

 by the new frustules, which are then produced. In the present 



