A tree crab's main body is about .25 meters (10 inches) across. They have 8 orifices, each ringed with teeth and four eyes (the entire creature has 24 eyes). They have eight limbs, which can bend in three directions but not rotate. The limbs are tipped with three-clawed pincers. These pincers act as both hands and feet for the crab. While individual pincers are not as versatile as human limbs, there are more of them, and when working in concert have finer control. While they don't have a natural front, back, top, or bottom, most orient themselves in one primary direction, much like handedness among humans. The ability to switch back and forth between dominant faces is considered quite acrobatic. Tree crabs are natural climbers, and are quite uncomfortable and awkward when not hanging or perking.
Tree Crabs navigate by sight and communicate by gestures and physical contact. The two forms of communication are separate: the tactile language can transfer information extremely rapidly, but can only be used to communicate to one other crab. The visual language is more akin to human languages in use and speed. They have an excellent sense of smell, but are nearly deaf. Tree Crabs have an odd idea of stealth: they can be quite noisy, but there is no 'behind' to sneak up on.
Tree crabs have a poor sense of abstraction, but good memories. They make up for this with a frightening dedication and a healthy imagination. They usually spend their entire life perfecting their knowledge and skills on a single subject, chosen rather randomly when young, and its often quite menial. On a familiar machine, a tree crab can work wonders.
Tree crabs are social creatures, and it is not uncommon for 40 individuals to share the same dwelling. They pool their resources. This works primarily because of their mating system. During each breeding season, each female chooses one male from their house to mate with. Each males strives to outperform the others in his “house” by bringing home as much as possible, or by making the house as pleasant as possible. This competition accelerates as mating season approaches, and visibly effects economies including tree crabs.
The interior of Tree Crab buildings looks like the structural scaffolding of some other races: a dense work of bars about one yard apart. The buildings are poorly lit by human standards, as the creatures are nocturnal.
Tree Crabs mature in only 10 or so years, but rarely live more than 40. This is likely due to their fast metabolism. Their natural diet is heavy on fruit, but they supplement that with meat (mostly insectiod type creatures).
Template[-30]ST -3 [-30], IQ-1 [-20], move -2 (ground only) [-5] Deafness [-20], Mute [-25], 360 degree vision , Brachiator , Discriminatory smell , Fine Manual DX , extra arm 1 (foot manipulator) , Night vision 2 , IT (no brain) , extra legs (four legs) , perk (talent cap at +1 above campaign standard) 
Most Tree crabs will have high levels of a talent, often customized. Aging has not been included as it is irrelevant in many campaigns. Social traits should be added by a GM after he builds a culture for them.
Role in CampaignTree crabs were designed as a 'laborer race'-- the classic use of them is to fill up the workyards of large cities with brute labor, machinists, and technicians. They fill an underclass role and they thrive as accepted but non-dominant members of a multi-species society.
They can also work as a stand alone polity or even as primitives. Such societies will be terribly alien to humans -- no sound, and cluttered with too many branches to move around properly. Tree crab societies will be centered in forests, likely in upper canopies-- they will not be able to live in deserts or plains. Its quite possible for them to share planets with others and maintain very separate societies.
A tree crab PC faces two large problems: communication and the abysmal ground move. In an environment where those are minimized, A tree crab can make a very capable character. As a species though, they are more suited to victory through numbers and using the right crab for the right job than through heroics.