The Collaborative International Dictionary
Dartos \Dar"tos\, n. [NL., fr. Gr. ? flayed.] (Anat.) A thin layer of peculiar contractile tissue directly beneath the skin of the scrotum.
Wiktionary
n. (context anatomy English) A thin layer of contractile tissue directly beneath the skin of the scrotum.
Wikipedia
The dartos fascia or simply dartos is a layer of connective tissue found in the penile shaft and scrotum. The penile portion is referred to as the superficial fascia of penis or the subcutaneous tissue of penis, while the scrotal part is the dartos proper. In addition to being continuous with itself between the scrotum and the penis, it is also continuous with Colles fascia of the perineum and Scarpa's fascia of the abdomen.
It lies just below the skin, which places it just superficial to the external spermatic fascia in the scrotum and to Buck's fascia in the penile shaft.
In the scrotum, it consists mostly of smooth muscle. The tone of this smooth muscle is responsible for the wrinkled (rugose) appearance of the scrotum.
In females, the same muscle fibers are less well developed and termed dartos muliebris, lying beneath the skin of the labia majora.
It receives innervation from postganglionic sympathetic nerve fibers arriving via the ilioinguinal nerve and the posterior scrotal nerve. (http://anatomy.med.umich.edu/gastrointestinal_system/inguinal_tables.html)
Usage examples of "dartos".
The dartos was a puzzle, the central spinal canal a myth, the decidua clothed in fable as much as the golden fleece.