Many thanks to those who responded re the validity of the genus Leptolyngbya.  Paul Silva provided a most comprehensive answer.  A number of people asked me to post the outcome so with Paul's permission, here is his response:

Leptolyngbya Anagnostidis et Komárek (in Arch. Hydrobiol. Suppl. 80 [Algol.
Stud. 50/53]: 390. 1988) was validly published with a designated type, L.
boryana (Gomont) Anagnostidis et Komárek (Phormidium boryanum Gomont). The
generic name was illegitimate, however, because the initial circumscription
of the genus included the type of Spirocoleus (Moebius ex Kirchner) Crow
(in Trans. Amer. Microscop. Soc. 46: 147. 1927). Noting that Leptolyngbya
had been widely used despite its recent publication, Compere (Taxon 46:
333. 1997) proposed that this name be conserved against Spirocoleus. This
proposal was recommended for approval by the Committee for Algae and
subsequently approved by the International Botanical Congress at St. Louis
in 1999. Leptolyngbya appears in the list of conserved generic names of
Cyanophyceae in the current edition (2000) of the International Code of
Botanical Nomenclature (p. 158).   

Spirocoleus, although rejected against Leptolyngbya, remains a legitimate
name available for use if its type is placed in a genus separate from the
type of Leptolyngbya. When the two types are placed in the same genus,
however, that genus must be called Leptolyngbya.   

Glenn McGregor
Scientist, Aquatic Ecosystem Health 
Natural Resource Sciences
Department of Natural Resources & Mines (NR&M)
1345 Ipswich Road

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