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



Marine: Bab el Mandeb! Seychelles! Madagascar! Pbilippines! Tahiti! Galapagos Islands! 

 Mazatlan (AtL), Cape Horn (Petit), Campeachy Bay (Atl.)- Fossil: Nankoori (Grrun.). 



78. D. Crabro Ehb. (1844). — V. constricted or not. L. 0,o4 to 0,2 mm.; B. 0,oi8 to 

 0,06 mm. Central nodule large, quadrate with parallel horns. Furrows narrow linear, with a row 

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

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

 toward the central nodule. 



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

 breadth of lunulae and in the amount, or absence, or constriction of the middle. The forms also 

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

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

 being more or less connected and differing 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, but the greater the number of intermediate forms observed, the greater be- 

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

 transitions from purely elliptical to strongly constricted forms, from forms with no lunulse to 

 others with broad lunulse; as to the ocelli I am not yet convinced of their value as specific cha- 

 racteristic. In most forms they occur as a marginal band, but there are forms without them, either 

 because they originally had none or because 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. 0,o8 

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

 Lunulse 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. Urn. A. S. Atl. XI 

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



Marine: Seychelles (Van Heurck Coll.)! Sumbava (Kinker Coll.)! Singapore! Java! China! 

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



The fig. 23 in A. S. Atl. is not sufficiently 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 costse. Otherwise, there is, as far as I can see, no difference. 



Var. Pandura Be]6b. (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 0,044 mm. Central nodule of 

 median size. Lunulse none. Costse 4 to 5 in 0, 01 mm. alternating with double rows of fine puncta 

 about 10 in 0,oi mm. — Nav. Pandura Br^b. D. de Cherb. f. 4. A. S. N. 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 D. von 

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

 Nav. Crabro Donk. B. D. p 46 PL VII f. 1. Nav. nitida Greg. T. M. S. IV p. 44 PL V f. 12*. 

 Nav. Mantichora Pant. Ill 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. navigans 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. 

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



Var. expleta 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,o3 mm. Costse 5 in 0,oi mm. alter- 



