1 Septa arranged hexamerally.........................................................................................................................2
- Septa arranged decamerally.......................................................................................................................11
2 Pedicel unattached; corallum cornute ................................................................... Crispatotrochus curvatus
- Pedicel attached; ceratoid to turbinate.........................................................................................................3
3 S1 larger than S2..........................................................................................................................................4
- S1 equal in width to S2................................................................................................................................5
4 Theca transverse ridged; S1 and S2 sinuous .......................................................... Crispatotrochus rugosus
- Theca not transversed ridge; S1 and S2 not sinuous ................................. Crispatotrochus septumdentatus
5 S1–2 with sinuous inner edges....................................................................................................................6
- S1–2 with straight inner edges.....................................................................................................................9
6 S3 with sinuous inner edges........................................................................................................................7 - S3 with straight inner edges..................................................................................... Crispatotrochus cornu
7 Columella fused, composed of closely united, poorly defined, twisted ribbons Crispatotrochus irregularis
- Columella with well defined columellar elements......................................................................................8
8 Septa arranged in four complete cycles; fossa nonextant ............................. Crispatotrochus galapagensis
- Septa arranged in five (complete) or six (incomplete) cycles; fossa moderately deep.................................. ............................................................................................................................ Crispatotrochus rubescens
9 Costae absent .......................................................................................................... Crispatotrochus niinoi
- Costae present (ridged or flat).................................................................................................................. 10
10 Columella composed of 4–7 broad, twisted laths; S5 present; costae slightly ridged near calicular edge......................................................................................................................................... Crispatotrochus foxi
- Columella composed of 28–32 narrow, twisted laths; S5 absent; costae flat ...... Crispatotrochus inortatus
11 S1 exsert.....................................................................................................................................................12
- S1 nonexsert .......................................................................................................... Crispatotrochus squiresi
12 Last septal cycle with serrate to lacerate inner edges................................................................................13
- Last septal cycle with entire inner edges..................................................................................................14
13 GCD = 6................................................................................................................. Crispatotrochus woodsi
- GCD> 6........................................................................................... C. sp. cf. C. cornu sensu Cairns, 1979
14 Adult stage with more than 3 cycles of septa (>40 septa)................................. Crispatotrochus gregarius
- Adult stage with three cycles of septa (= 40 septa)......................................... C. sp. A sensu Cairns, 1982