KONOI,. SV. VKT. AKADKMIENS II ANDLINGAH. BAND 27. N:(> 3. Ill 



This species is very vai'iable and ootnprises a number of forms, wliicli liowevc]' are so closely 

 connected, that I am unable, after comparison of a large number of sketches, to group them in 

 separate species or varieties. Besides, tlie form, and appearance of the valve, especially of the 

 ends, changes much according to its position. Tlie ventral side, which in lai'ger specimens has a 

 row of shoi't costate striic, has in some forms a few striic, at the ends only and in others none at 

 all. The double rows of puncta alternating with the costic. are in some specimens not distinct. 

 Smaller foi'ms are closely connected with A. crassa var. spuria. 



<). A. tesselata Grovb: and Stukt (1S87). — V. linear, with inwards curved, obtuse ends. 

 L. <l, lu; B. 0,(1 If) mm. Median line biarcuate. Dorsal side with strong, smooth transverse costa;, 

 5,5 in 0,0 1 mm. crossed by longitudinal costie, about 7 in 0,01 mm. Ventral side with coarse, 

 costate strict. — Q. M. CI. Ill (2) p. 131 PI. X f . I. 



Marine: Oamaru, N. Zealand, fossil! 



This peculiar form seems to me certainly to belong to the group of A. crassa, but differs 

 from all other forms by its peculiar structure. The dorsal side of the valve seems to be covered 

 with quadrate alveoli, disposed in transverse and hingitudinal rows. The specimens I have seen were 

 mounted in a position, not favourable for examination of the ventral side. Still I succedeed by 

 means of very oblique light in seeing on the ventral side, a row of strong, costate striae and on 

 the dorsal side not far from the median line a longitudinal line, the space between the lines being 

 crossed by transverse costate striae. 



7. A. iiielegjiiis Cl. and Grove (1891). — V. sulilunate, with incurved, obtuse ends. L. 0,o9; 

 B. 0,0 3 mm. Median line biai'cuate. Axial and central areas indistinct on the dorsal and ventral 

 side. Dorsal side with 7 costate striae in 0,oi mm. crossed by a narrow, blank longitudinal line. 

 Ventral side without central area and with strong, costate stri*., divergent, between the central 

 nodule and the ends, towards the median line. — Diatomiste 1 p. 68 PI. X f. IT). 



Marine: Macassar Straits! 



Var.? polito, Cl. -- V. stout, elongated, with broad, obtuse and incurved ends. L. 0,o6; 

 B. 0,0 ir> mm. Median line biarcuate. Dorsal side with strong, smooth, costate stria;, 6 in 0,oi 

 mm., reaching to the median line and crossed by a narrow, blank line. Ventral side with rounded 

 central area and strong, costate striae, crossed by a narrow, blank line. — PI. IV f. 40. 



Marine: .fava! 



This form is very dissimilar to the type, but it is difficult to find any specifically distinct 

 characteristic. 



8. A. ornatsi Leud. Fortm. (1879). — V. linear, with incurved, obtuse ends. L. 0, i; B. 0,o2 

 mm. Dorsal side with 8 costate strite in 0,0 1 mm. crossed by a linear furrow and reaching to the 

 median line. Ventral side witli inclined rows (7 in 0,oi mm.) of puncta, crossed by a longitudinal, 

 narrow area. — D. de Ceylon p. 20 PI. I f. 9. 



Marine: Ceylon (Le Tourneur Coll.)! 



I have seen a single valve only, the opaque structure of which did not admit of a close 

 examination of the dorsal side. Still there can be no doubt that this form is a distinct species, 

 belonging to the group of A. crassa. 



9. A. comorensis Cl. N. sp. — V. broadly linear, with obliquely rounded and slightly 

 incurved ends. L. 0,i4 to 0,iy; B. 0,02r) mm. Median line strongly biarcuate and elevated. Dorsal side 

 with ti^ansverse rows (7 in 0,oi mm.) of large puncta (10 in 0,oi mm.) not reacliing to the median 

 line. Ventral side with curved rows of large and distant puncta, crossed by a narrow blank area. 



Marine: Nossibe (Brun Coll.)! Tamatave (Kinker Coll.)! 



This is a large and distinct form, akin to A. ornafa. The opaque structure and the eleva- 

 tion to a keel of the median line made the examination of the dorsal side difficult. Still I believe 

 that the dorsal rows of puncta are crossed by a keel or longitudinal line. 



