Solen sicarius Gould, 1850 Common name(s): Jackknife clam, sickle jackknife clam, sickle razor clam, blunt razor clam, fast jackknife clam
Synonyms:
Phylum Mollusca  Class Bivalvia Subclass Heterodonta  Order Veneroida  Family Solenidae
	Solen sicarius, 5 cm long, dug out of mud in the low intertidal of March Point, Padilla Bay. Ventral (see top) and dorsal (see lower) views. The anterior end is to the left in both photos. Note the siphons slightly protruding from the posterior end, and that the posterior end is more rounded than the posterior end. The dorsal side (see lower view) is slightly concave in profile.
	(Photos by:  Dave Cowles, July 2026)

Description:  This species, the only member of its family Solenidae in this area, is a small, long, slender clam with a smooth, shiny periostracum  that projects only very slightly if at all beyond the calcified portion of the shell.The shell itself is quite thin and about 4 times as long as high. The periostracum is glossy yellowish brown or yellowish-green, ususlly of several different shades.The shell gapes at both ends and dark-speckled extensions of the mantle bridge the gap between the shells olong the ventral margin (see photo above). The shell interior is dull blue and white and has two adductor muscle scars of similar size. The dorsal side of the shell is slightly concave along the entire length of the shell (photo), and the anterior end of the shell is blunter than the posterior. The hinge ligament is external and the hinge and the beak are near the anterior end. The foot is dark. The siphons are united. Length up to 12.5 cm.

How to Distinguish from Similar Species:  This distinctive-looking clam is likely to be mistaken for only a few other local species due to its streamlined shape, its glossy-smooth periostracum, and its distinctive color. All the other similar clams are less than 3x as long as high and do not have a concave dorsal margin. The razor clam Siliqua patula is much larger as an adult, growing as large as 18 cm. long. It lives in sandy areas. The gutless awning clam, Solemya reidi, grows up to 6 cm long and lives in highly organic, strongly anoxic subtidal muds. Its periostracum extends substantially beyond the calcified margin of its shell. Solen rosaceus lives farther south in southern California and has a straight profile along its dorsal side. 

Geographical Range:  British Columbia to northern Baja California

Depth Range:  Intertidal to 54 m. Usually subtidal

Habitat:  Muddy sand, sometimes in eelgrass, in sheltered areas.

Biology/Natural History:  Tends to make lasting vertical burrows about 30 cm deep into hard-packed mud. It can dig rapidly. Pea crabs are often found residing in the clam's mantle cavity. This clam is said in Ricketts et al. 1985 to be able to jump, to dig into the mud within 30 seconds, and to swim by rapidly expelling water from its posterior siphons or from an anterior opening in the mantle near the foot (presumably letting it swim either forward or backward). It is presumed to use these unusual skills to escape from predators, and jetting water from the  anterior end may also aid in digging its burrow. It may also autotomize (break off) the end of its siphons when disturbed.

References:

General References:
  Abbott, 1986
  Harbo, 2001
  Kozloff, 1993
  Lamb and Hanby, 2005
  Morris, 1966
  Morris et al., 1980
  Rice, 1972
  Ricketts et al., 1985

Scientific Articles:
 

Web sites:

General Notes and Observations: Locations, abundances, unusual behaviors:

A close-up view of the squared-off anterior end. Note that the beak, visible at the top, is at the extreme anterior end. Photo by Dave Cowles, July 2026

The posterior end (seen with siphons partly extended) is more rounded. Photo by Dave Cowles, July 2026 

The dorsal side (upper side in this photo) is slightly concave. The beak is at the anterodorsal corner, at the top left in this photo. Photo by Dave Cowles, July 2026

This individual, collected by benthic grab from a muddy bottom at about 6 m depth in the Padilla Bay boat channel next to March Point, is 2 cm long and a reddish-brown color. The dorsal margin of the shell of this individual is almost straight. Photo by Dave Cowles, July 2026

Authors and Editors of Page:
Dave Cowles (2026):  Created original page
CSS coding for page developed by Jonathan Cowles

Salish Sea Invertebrates web site provided courtesy of Walla Walla University