100 P. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



Marine: Bab el Mandeb! Seyclielles! Madagascar! Philippines I Tahiti! Gralapagos Islands 1 

 Mazatlan (Atl.), Cape Horn (Petit), Campeacliy Bay (Atl.). Fossil: Nankoori (Grun.). 



78. D. Crabro Ehb. (1844). — V. constricted or not. L. 0,04 to 0,2 mm.; B. 0,oi8 to 

 0,06 mm. Central nodnle large, quadrate with parallel horns. Fnrrows narrow linear, with a row 

 of large pnncta. Lunulai none or more or less large. Costse 3 to 8 in 0,oi mm. alternating with 

 double rows of alveoli outside of the Innnlse. Ocelli forming a marginal band, bent inwards 

 toward the central nodnle. 



This species comprises a considerable number of forms, differing in size, number of costte., 

 breadth of Innnlte. and in the amonnt, or absence. or constriction of the middle. The forms also 

 present a very different appearance, according as they are nninjured or corroded. Having com- 

 pared a very large nnmber of diiferent forms I am unable to make distinct species of them, all 

 being more or less connected and ditfering only in characteristics, which are .subject to great 

 variation. 



If only a few extreme forms be examined, it is easy to found on them apparently well 

 defined species, bnt the greater the number of intermediate forms observed, the greater be- 

 comes the difficnlty of finding any definite distinctions between them. There are all intermediate 

 transitions from purely elliptical to strongly constricted forms, from forms with no Innul» to 

 others vpith broad Innnlffi; as to the ocelli I am not yet convinced of their value as specilic cha- 

 racteristic. In most forms they occnr as a marginal band, bnt there are forms withont them, either 

 because they originally had none or becanse the ocelli have been destroyed in preparation. 



I have distinguished the following forms, which diatomists, fond of speciesmaking, may 

 consider as specifically distinct. 



A. Forms with no, or very narrow lunulce. 



Var. Umitanea A. S. (1875). — V. panduriform, with narrow elliptical segments. L. O, os 

 to 0,1 1; B. 0,024 to 0,032, at the constriction 0,oi7 to 0, 025 mm. Central nodnle small, quadrate. 

 Lunulfe very narrow. Costse 6 to 7 in 0,oi mm. alternating with double rows of alveoli, about 

 14 in 0,01 mm. Ocelli forming a narrow band along the margin. — Nav. lim. A. S. Atl. XI 

 f. 23, LXIX f. 14 (optime) (not f. 12). 



Mai-ine: Seychelles (Van Heurck Coll.)! Sumbava (Kinker CoU.)! Singapore! Java! China! 

 Kergnelens Land! Fossil: Atlantic City N. Jers. (Deby Coll.)! 



The fig. 23 in A. S. Atl. is not snfficiently characteristic, but the fig. 14 Pl. LXIX repre- 

 sents very well the form, which I understand to be Umitanea. It differs from Var. Pandura by 

 smaller size and closer costte. Otherwise, there is, as far as I can see, no difference. 



Var. Pandura Bréb. (1854). — V. constricted, with elongated, tongue-shaped segments. 

 L. 0,106 to 0,212; B. 0,038 to 0,053; at the constriction 0, 023 to 0,o44 mm. Central nodnle of 

 median size. Lunulfe none. Costee 4 to 5 in 0, 01 mm. alternating with double rows of fine pnncta 

 abont 10 in 0,oi mm. — Nav. Pandura Bréb. D. de Cherb. f. 4. A. S. X. S. D. Pl. II f. 3 

 (optime!) Atl. XI f 1, 2, 9 (4, 8 corroded). V. H. Syn. Pl. IX f. 1. Truan and Witt I), von 

 Jeremie Pl. IV f. 14 (corroded). Pinnul. Pandura var. elongata Greg. D. of Clyde Pl. IX f. 22. 

 Nav. Crahro Donk. B. D. p 46 Pl. VII f. 1. Nav. niiida Greg. T. M. S. IV p. 44 Pl. V f 12*. 

 Nav. Mantichora Pant. III Pl. XXXV f. 490; 1893 (corroded). 



Marine: North Sea! Mediterranean Sea! Adriatic! Red Sea! Madagascar! Sumbava! Society 

 Islands! Galapagos Islands! Magellhaens Strait! Bolivia! Campeachy Bay! West Indies! 



As Nav. naviyans Brun a form has been figured in A. S. Atl. CLXXIV f. 1, which seems 

 to belong to Var. Pandura. The figure is too indistinct for Identification. Perhaps fig. 3, Nav. 

 sidcralis A. S., may be the some form in a very corroded state. 



Var. expleia A. S. (1881). — V. slightly constricted, with broad, tongue-shaped segments. 

 L. 0,07 to 0,12; B. 0,032 to 0,033; at the constr. 0,027 to 0, 03 mm. Costse 5 in O.oi mm. alter- 



