Pattyclaya / Elysia cf arena

April 26, 2006
From: Cynthia Trowbridge

Dear Bill,

Hi! In November or December 2005, the Hiranos and I found this species or a closely related undescribed "Pattyclaya " species on the west coast of Okinawajima (main island of Okinawa).

Three points:

1. In message #16395, you asked about the demise of the genus name Pattyclaya... it was in Gosliner (1995). Terry stated "Continued usage of the genera Elysiella, Plattyclaya [should be Pattyclaya], Tridachia and Tridachiella renders Elysia paraphyletic..." p. 1.

2. Hamatani (2000) reported Pattyclaya sp. from Okinawa (pp. 764-765). Regretfully, Hamatani has not yet published why he considered it different from P. arena. Clay suggested to me that Hamatani felt there were differences in coloration.

3. To be conservative, we are calling our Okinawa species Elysia cf. arena. Externally our species has the same general appearance and pattern of parallel transverse lamellae inside the parapodia as Elysia arena Carlson & Hoff (1977). Once we dissect the radula and examine the species in more detail, we will let you know: if our species is E. arena, then our record will represent a range extension from the type locality.

  • Gosliner, T.M. (1995) The genus Thuridilla... Proc. Calif. Acad. Sci. 49(1): 1-54.
  • Hamatani (2000) in Marine mollusks in Japan edited by Takashi Okutani. Tokai Daigaku Shuppankai, Tokyo.


Trowbridge, C.D., 2006 (Apr 26) Pattyclaya / Elysia cf arena. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Cynthia,
Thanks for your response. As you will see Clay & Patty-Jo have sent some photos of  P. arena and Corey Whisson has sent a nice photo showing the transverse lamellae in P. brycei. As I said in reply to his message I remembered Terry's paper soon after posting my query. I am being even more conservative than you in retaining Pattyclaya, at least temporarily. It would be interesting if you do have another species of this transverse lamellae group.
Best wishes,
Bill Rudman

Rudman, W.B., 2006 (Apr 26). Comment on Pattyclaya / Elysia cf arena by Cynthia Trowbridge. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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