Key:  Family Spirorbidae

Taken primarily from  Kozloff, 1987, 1996 p. 164 (Copyright 1987, 1996, University of Washington Press.  Used in this web page by permission of University of Washington Press)

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1a	Coiling of tube mainly dextral (the tube coils in a counterclockwise direction from the closed end of the tube when it is viewed from the exposed side, which is ventral) (photo)	2
1b	Coiling of the tube sinestral (the tube coils in a clockwise direction from the closed end of the tube when it is viewed from the exposed side)	7
2a	Embryos attached to the inside of the tube	3
2b	Embryos attached to, or associated with, the outside of the tube	6
3a	Embryos in a string attached to the inside of the tube; tube not transparent (coiling of the tube sinestral in most California populations, but dextral in more northern populations; intertidal	Spirorbis bifurcatus
3b	All embryos attached singly to the inside of the tube; tubes may or may not be transparent	4
4a	Tube of adult animals porcelaneous or translucent, but not transparent to the extent that the animal and embryos can be seen	5
4b	Tubes of adult animals transparent, revealing red embryos (juveniles have somewhat opaque tubes) (intertidal and subtidal on hard substrata; coiling primarily dextral, but some sinestral coiling has been observed)	Paradexiospira (Spirorbides) vitrea
5a	Tube opaque and porcelaneous; intertidal and subtidal on hard substrata or on algae (coiling dextral, except in some California populations)	Circeis armoricana
5b	Tube translucent; subtidal and only on bryozoans and hydroids	Circeis spirillum
6a
6b
7a
7b
8a
8b
9a
9b
10a
10b
11a
11b
12a
12b
13a
13b

  Circeis spirillum

Salish Sea Invertebrates web site provided courtesy of Walla Walla University