Transverse section of body of female lobster in plane of gastric mill..... ad. m. abductor mandibuli muscle; art, branchio-cardiac vessel; arth. br., arthrobranch; br. cav., branchal cavity; brs, branchiostegite; d. g. g. duct of gastric gland; fl. g. ch. based flexor of great chelipad; g. g. gastric gland; int. s. internal skeleton in roof of sternal sinus; n. (x), main nerve of great cheliped; p. g. m. i., first division of posterior gastric muscle; p. br., pleurobranch; Podo br., posobranch; i. ad. m., tendon of abductor mandibull muscle; th. fl, floor of thoracic cavity.