1. Calcareous ring with posteriorly forked radial plates always in combination with large multi-layered, reticulated plates or lenslike bodies as major body wall deposits; Indo-Pacific forms...................................... Leptopentacta... 2
- Calcareous ring usually with unforked radial plates in combination with usually large unreticulated, smooth plates made up of a single layer of calcareous material, as major body wall deposits; Mediterranean and North-West Atlantic forms...................................................................................... Paraleptopentacta n. gen.... 7
2. External layer of deposits exclude baskets or rosettes of any form............................................... 3
- External layer of deposits include baskets or rosettes or both................................................... 4
3. Tube feet rigid, non-retractile; only small knobbed buttons present in addition to reticulated plates......... L. bacilliformis
- Tube feet retractile; knobbed buttons present; plates complex with reticulated bars (species known only from juveniles)................................................................................................... L. nina
4. External layer of ossicles as rosettes developed from baskets, complete baskets often present in addition to rosettes, perhaps in juveniles only............................................................................... L. imbricata
- External layer of ossicles only as baskets................................................................... 5
5. Baskets deep, cup-like; plates as lens-like, reticulated bodies; smaller, smooth plates and knobbed buttons with large holes also present........................................................................................ L. grisea
- Baskets also deep, cup-like; large plates reticulated but not appearing as lenticular or lens-like bodies; other plates also present but also non-lenticular; buttons present.................................................................... 6
6. Some baskets rosette-like; buttons knobbed with small holes; reticulate plates never with a protruding spine..................................................................................................... L. punctabipedia
- Baskets deep, cup-like; sometimes both baskets and plates provided with a protruding spine................. L. panamica
7. Plates smooth, simple, multilocular, of several sizes, rarely imbricating; baskets numerous, variable.................... 8
- Plates of various forms, rarely one or two reticulate; baskets flat, with trabeculae, margins slightly knobbed...... P. cucumis
8. Baskets large, with numerous marginal projections, buttons absent from body wall; large plates smooth................. 9
- Baskets tiny but also with numerous projections; buttons also tiny, knobbed, holes minute; large plates knobbed..................................................................................................... P. djakonovi
9. Plates smooth, imbricating; baskets with tiny projections and sometimes multilocular base; plates of various sizes but never narrow and elongate, holes large; rosettes absent..................................................... P. elongata
- Plates not imbricating, smooth, of various sizes, often narrow with usually two series of small holes; baskets cup-like, with numerous projections in various directions; rosettes also present............................... P. tergestina n. comb.