Luticola mobiliensis

Valves are large and linear-lanceolate, becoming barely triundulate in larger specimens. Apices are cuneate. Striae are radiate, becoming more dense near the apices. The central area is transversely oriented, incomplete, and characterized by a distinct stigma with a slit-like external opening. Few to many puncta are erratically scattered throughout the central area. The axial area is narrow and linear. Longitudinal lines are visible along the valve margins. The raphe is mostly lateral, with hooked distal ends and inflated proximal ends deflected to one side. Areolae are coarse and easily visible in LM, measuring 16-18 in 10 µm.

NOTES:

Details on the Boyer material are worth documenting here. Boyer did not designate a holotype specimen, although there is an LM photograph in his publication (Boyer 1922), as shown below. Based on Boyer’s notes kept at the ANSP, the type material of Navicula mobiliensis is the slide 747 in Boyer Collection. Careful scanning of the slide showed that only one complete valve of N. mobiliensis was present on the slide and it is the specimen illustrated by Boyer (1922). This same specimen was circled and designated as lectotype by Reimer et al. (1991). Examination of the publication by Reimer et al. (1991) leads us to believe that Reimer was not sure that the specimen found on slide 747 was identical to that photographed by Boyer, and therefore designated it as a lectotype. He also designated two isotypes (slides ANSP Boyer Coll. 1041 – circled specimen, and GC 2955 – no specimen selected). Reimer et al. (1991), however, appear to have made an error, as only the original author is able to designate an isotype. Identification of the holotype specimen means that Reimer’s isotypes should be rededicated to epitypes.

The holotype specimen was illustrated by a drawing in Patrick and Reimer (1966, Pl. 42/p. 548, Fig. 11), without any indication of the type status. The same specimen was also illustrated by a photograph in Mayama and Kawashima (1998, Fig. 2), who transferred N. mobiliensis to the genus Luticola. The authors, however, did not know they were publishing an image of the holotype and did not mention the word “lectotype” (or any other type) for this specimen in the publication. Based on current knowledge, label on the specimen shown in Fig. 2 should have been the “holotype (incorrectly designated as lectotype by Reimer et al. 1991)”. Mayama and Kawashima (1998) also showed another photograph of N. mobiliensis (in Fig. 1) and labeled it as the “isotype” (from slide GC 2955). This image should have been described as “a specimen from an epitype slide (incorrectly designated as isotype by Reimer et al. 1991)”.