retinaculum

Small hook at tip of appendices internae (e.g., Caridea), one of many serving to join left and right pleopods together. (Pl. retinacula) (Syn. cincinnulus) [Moore and McCormick, 1969].

Small hook at tip of appendix interna, one of many serving to interlock right and left pleopods. (Pl. retinacula) (Syn. cincinnulus) [McLaughlin, 1980].

(Order Cumacea):

In first pair of maxillipeds, one of several small, hook-like structures along inner margin of basis. Serves to interlock left and right maxillipeds. (Syn. coupling hook) [Stachowitsch, 1992].

(Order Isopoda):

In maxilliped, one in a series of small, hook-like structures along margin of endite of second segment (basis). Serves to interlock left and right maxillipeds. (Syn. coupling seta, coupling hook) [Stachowitsch, 1992].

(Order Stomatopoda):

One in a series of hooks on appendix interna of each abdominal appendage (pleopod); interlocks with retinacula of second member of pleopod pair and permits both pleopods to move in unison [Stachowitsch, 1992].

(Superorder Syncarida):

In male anaspidacean, one in a series of small, hook-like structures along inner branch (endopod) of modified first and second pairs of pleopods. Serves to interlock left and right pleopods [Stachowitsch, 1992].