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Ischnochiton (Ischnochiton) elongatus (Blainville, 1825)

Description: Animal narrowly ovate, girdle moderately broad. Median valves with lateral and pleural areas well differentiated; lateral areas raised, varying from smooth to moderately strongly ribbed; pleural areas, without magnification, smooth, with magnification covered with dense, curved threads. Girdle densely covered with medium size, ridged scales up to 0.22 mm wide. Colour extremely variable; uniformly creamy white, buff, dark orange, reddish brown or dark green, light coloured with darker dots, often with a broad white stripe central on the dorsum, or with an irregular pattern of dark stripes.

Size: Up to 36 mm in length.

Distribution: Endemic to Australia: Burleigh Heads, Qld, southwards and around southern Australia to Shark Bay, WA, including Tas.

Habitat: Lives in the low intertidal and subtidal under rocks and stones.

Comparison: There are three NSW species of the subgenus Ischnochiton (Ischnochiton). Their colour patterns are very variable, but each has patterns which are variations on a few basic themes and are different to the themes of other species. The three species have striated girdle scales which differ in size, providing a more useful character for identification.

  Girdle scale width Max. animal length
I. examinandus 0.11 mm 15 mm
I. elongatus 0.22 mm 36 mm
I. versicolor 0.48 mm 60 mm


Synonymy: The subspecific name Ischnochiton elongatus crispus (Reeve, 1847) has been used for eastern Australian specimens on the basis that the girdle scales are slightly larger than in southern specimens. This is a minor character on which to base a subspecies, and the name is best not used.

Fig. 1:  l. Arrawarra, N. of Woolgoola, NSW (C.347106) r. Murrumbulga Point, Twofold Bay, NSW (C.347125).

Fig. 2: More colour varieties.

Fig. 3: Bulli Point, NSW (C.563413).  More colour varieties

Fig. 4: Toowoon Bay, NSW (DLB5596). Detail of valve sculpture.

Fig. 5: Toowoon Bay, NSW (DLB5596). Detail of scales.


Copyright Des Beechey 2019